strpos

Just a quick note, if by some chance you pass an array to strpos function you might have unexpected behaviour.

<?php
$foobar = array();

if(strpos($foobar, 'something') !== false) {

}
?>

The above condition will actually pass and execute your code.

This functions throws an "Offset not contained in string" error if the offset is not in between 0 and the length of string.

A strpos modification to return an array of all the positions of a needle in the haystack 

<?php
function strallpos($haystack,$needle,$offset = 0){
    $result = array();
    for($i = $offset; $i<strlen($haystack); $i++){
        $pos = strpos($haystack,$needle,$i);
        if($pos !== FALSE){
            $offset =  $pos;
            if($offset >= $i){
                $i = $offset;
                $result[] = $offset;
            }
        }
    }
    return $result;
}
?>

example:-

<?php
$haystack = "ASD is trying to get out of the ASDs cube but the other ASDs told him that his behavior will destroy the ASDs world";

$needle = "ASD";

print_r(strallpos($haystack,$needle));

//getting all the positions starting from a specified position

print_r(strallpos($haystack,$needle,34));
?>

if you want to get the position of a substring relative to a substring of your string, BUT in REVERSE way:

<?php

function strpos_reverse_way($string,$charToFind,$relativeChar) {
    //
    $relativePos = strpos($string,$relativeChar);
    $searchPos = $relativePos;
    $searchChar = '';
    //
    while ($searchChar != $charToFind) {
        $newPos = $searchPos-1;
        $searchChar = substr($string,$newPos,strlen($charToFind));
        $searchPos = $newPos;
    }
    //
    if (!empty($searchChar)) {
        //
        return $searchPos;
        return TRUE;
    }
    else {
        return FALSE;
    }
    //
}

?>

A pair of functions to replace every nth occurrence of a string with another string, starting at any position in the haystack. The first works on a string and the second works on a single-level array of strings, treating it as a single string for replacement purposes (any needles split over two array elements are ignored).

Can be used for formatting dynamically-generated HTML output without touching the original generator: e.g. add a newLine class tag to every third item in a floated list, starting with the fourth item.
 
<?php
/* String Replace at Intervals   by Glenn Herbert (gjh42)    2010-12-17
 */
 
//(basic locator by someone else - name unknown)
//strnposr() - Find the position of nth needle in haystack.
function strnposr($haystack, $needle, $occurrence, $pos = 0) {
    return ($occurrence<2)?strpos($haystack, $needle, $pos):strnposr($haystack,$needle,$occurrence-1,strpos($haystack, $needle, $pos) + 1);
}

//gjh42
//replace every nth occurrence of $needle with $repl, starting from any position
function str_replace_int($needle, $repl, $haystack, $interval, $first=1, $pos=0) {
  if ($pos >= strlen($haystack) or substr_count($haystack, $needle, $pos) < $first) return $haystack;
  $firstpos = strnposr($haystack, $needle, $first, $pos);
  $nl = strlen($needle);
  $qty = floor(substr_count($haystack, $needle, $firstpos + 1)/$interval);
  do { //in reverse order
    $nextpos = strnposr($haystack, $needle, ($qty * $interval) + 1, $firstpos); 
    $qty--;
    $haystack = substr_replace($haystack, $repl, $nextpos, $nl);
  } while ($nextpos > $firstpos);
  return $haystack;
}
  //$needle = string to find
  //$repl = string to replace needle
  //$haystack = string to do replacing in
  //$interval = number of needles in loop
  //$first=1 = first occurrence of needle to replace (defaults to first) 
  //$pos=0 = position in haystack string to start from (defaults to first) 
 
//replace every nth occurrence of $needle with $repl, starting from any position, in a single-level array
function arr_replace_int($needle, $repl, $arr, $interval, $first=1, $pos=0, $glue='|+|') {
  if (!is_array($arr))  return $arr;
  foreach($arr as $key=>$value){
    if (is_array($arr[$key])) return $arr;
  }
  $haystack = implode($glue, $arr);
  $haystack = str_replace_int($needle, $repl, $haystack, $interval, $first, $pos);
  $tarr = explode($glue, $haystack);
  $i = 0;
  foreach($arr as $key=>$value){
    $arr[$key] = $tarr[$i];
    $i++;
  }
  return $arr;
}
?>
If $arr is not an array, or a multilevel array, it is returned unchanged.

The Situation:

I wanted to return TRUE if strpos returned position 0, and only position 0, without the added overhead of preg_match.

The Solution:

As PHP treats 0 (zero) as NULL, and strpos returns the int 0 (but not NULL), I used type casting and the "===" comparison operator (as it compares types) to resolve my issue.

<?php

$hayStack = "dbHost";
$needle  = "db"
$needlePos = strpos($hayStack, $needle);

if((string)$needlePos === (string)0) {
    echo "db is in position zero";
} else {
    echo "db is NOT in position zero";
}

?>

Returns:
db is in position zero

<?php

$hayStack = "another_db_host";
$needle  = "db"
$needlePos = strpos($hayStack, $needle);

if((string)$needlePos === (string)0) {
    echo "db is in position zero";
} else {
    echo "db is NOT in position zero";
}

?>

This returns:
db is in NOT position zero

This might be useful.

<?php
class String{
    
    //Look for a $needle in $haystack in any position
    public static function contains(&$haystack, &$needle, &$offset)
    {
        $result = strpos($haystack, $needle, $offset);
        return $result !== FALSE;
    }
    
    //intuitive implementation .. if not found returns -1.
    public static function strpos(&$haystack, &$needle, &$offset)
    {
        $result = strpos($haystack, $needle, $offset);
        if ($result === FALSE )
        {
            return -1;
        }
        return $result;
    }
    
}//String
?>

WARNING

As strpos may return either FALSE (substring absent) or 0 (substring at start of string), strict versus loose equivalency operators must be used very carefully.

To know that a substring is absent, you must use:  

=== FALSE

To know that a substring is present (in any position including 0), you can use either of:

!== FALSE  (recommended)
 > -1  (note: or greater than any negative number)

To know that a substring is at the start of the string, you must use:  

=== 0

To know that a substring is in any position other than the start, you can use any of: 

 > 0  (recommended)
!= 0  (note: but not !== 0 which also equates to FALSE)
!= FALSE  (disrecommended as highly confusing)

Also note that you cannot compare a value of "" to the returned value of strpos. With a loose equivalence operator (== or !=) it will return results which don't distinguish between the substring's presence versus position. With a strict equivalence operator (=== or !==) it will always return false.

This is a bit more useful when scanning a large string for all occurances between 'tags'.

<?php
function getStrsBetween($s,$s1,$s2=false,$offset=0) {
    /*====================================================================
    Function to scan a string for items encapsulated within a pair of tags

    getStrsBetween(string, tag1, <tag2>, <offset>

    If no second tag is specified, then match between identical tags

    Returns an array indexed with the encapsulated text, which is in turn
    a sub-array, containing the position of each item.

    Notes:
    strpos($needle,$haystack,$offset)
    substr($string,$start,$length)

    ====================================================================*/

    if( $s2 === false ) { $s2 = $s1; }
    $result = array();
    $L1 = strlen($s1);
    $L2 = strlen($s2);

    if( $L1==0 || $L2==0 ) {
        return false;
    }

    do {
        $pos1 = strpos($s,$s1,$offset);

        if( $pos1 !== false ) {
            $pos1 += $L1;

            $pos2 = strpos($s,$s2,$pos1);

            if( $pos2 !== false ) {
                $key_len = $pos2 - $pos1;

                $this_key = substr($s,$pos1,$key_len);

                if( !array_key_exists($this_key,$result) ) {
                    $result[$this_key] = array();
                }

                $result[$this_key][] = $pos1;

                $offset = $pos2 + $L2;
            } else {
                $pos1 = false;
            }
        }
    } while($pos1 !== false );

    return $result;
}
?>

My version of strpos with needles as an array. Also allows for a string, or an array inside an array.

<?php
function strpos_array($haystack, $needles) {
    if ( is_array($needles) ) {
        foreach ($needles as $str) {
            if ( is_array($str) ) {
                $pos = strpos_array($haystack, $str);
            } else {
                $pos = strpos($haystack, $str);
            }
            if ($pos !== FALSE) {
                return $pos;
            }
        }
    } else {
        return strpos($haystack, $needles);
    }
}

// Test
echo strpos_array('This is a test', array('test', 'drive')); // Output is 10

?>

The most straightforward way to prevent this function from returning 0 is:

  strpos('x'.$haystack, $needle, 1)

The 'x' is simply a garbage character which is only there to move everything 1 position.
The number 1 is there to make sure that this 'x' is ignored in the search.
This way, if $haystack starts with $needle, then the function returns 1 (rather than 0).

A function I made to find the first occurrence of a particular needle not enclosed in quotes(single or double). Works for simple nesting (no backslashed nesting allowed).

<?php
function strposq($haystack, $needle, $offset = 0){
    $len = strlen($haystack);
    $charlen = strlen($needle);
    $flag1 = false;
    $flag2 = false;
    for($i = $offset; $i < $len; $i++){
        if(substr($haystack, $i, 1) == "'"){
            $flag1 = !$flag1 && !$flag2 ? true : false;
        }
        if(substr($haystack, $i, 1) == '"'){
            $flag2 = !$flag1 && !$flag2 ? true : false;
        }
        if(substr($haystack, $i, $charlen) == $needle && !$flag1 && !$flag2){
            return $i;        
        }
    }
    return false;
}

echo strposq("he'llo'character;\"'som\"e;crap", ";"); //16
?>

beware the mindless "if needle is not string" :

root@voice1:/www/voice_ed#php -r 'var_dump(strpos("X1234567",5));'
bool(false)
root@voice1:/www/voice_ed#php -r 'var_dump(strpos("X1234567","5"));'
int(5)
root@voice1:/www/voice_ed#

Parse strings between two others in to array.

<?php
function g($string,$start,$end){
     preg_match_all('/' . preg_quote($start, '/') . '(.*?)'. preg_quote($end, '/').'/i', $string, $m);
     $out = array();

     foreach($m[1] as $key => $value){
       $type = explode('::',$value);
       if(sizeof($type)>1){
          if(!is_array($out[$type[0]]))
             $out[$type[0]] = array();
          $out[$type[0]][] = $type[1];
       } else {
          $out[] = $value;
       }
     }
  return $out;
}
print_r(g('Sample text, [/text to extract/] Rest of sample text [/WEB::http://google.com/] bla bla bla. ','[/','/]'));
?>

results:
Array
(
    [0] => text to extract
    [WEB] => Array
        (
            [0] => http://google.com
        )

)

Can be helpfull to custom parsing :)

I found that whatever I was using as a test with strpos it came out false exept if $pos was == 1

I figured it gives me a numeric value if found else it is null or false
here is what i did to make my code work:

<?php
//EXAMPLE 1:
$quiamime = ',64,68,70,';
$me = '64'
$posi = strpos($quiaime, ",$me,");  //posi is equal to 0
if (!is_numeric($posi)){
 //code here
}else{
  //else code here
}

//EXAMPLE 2:
$quiamime = ',68,70,64,';
$me = '64'
$posi = strpos($quiaime, ",$me,");  //posi is equal to 6
if (!is_numeric($posi)){
 //code here
}else{
  //else code here
}

//EXAMPLE 3:
$quiamime = ',68,70,';
$me = '64'
$posi = strpos($quiaime, ",$me,");  //posi is equal to NULL or FALSE
if (!is_numeric($posi)){
 //code here
}else{
  //else code here
}
?>

This function finds postion of nth occurence of a letter starting from offset.

<?php
function nth_position($str, $letter, $n, $offset = 0){
    $str_arr = str_split($str);
    $letter_size = array_count_values(str_split(substr($str, $offset)));
    if( !isset($letter_size[$letter])){
        trigger_error('letter "' . $letter . '" does not exist in ' . $str . ' after ' . $offset . '. position', E_USER_WARNING);
        return false;
    } else if($letter_size[$letter] < $n) {
        trigger_error('letter "' . $letter . '" does not exist ' . $n .' times in ' . $str . ' after ' . $offset . '. position', E_USER_WARNING);
        return false;
    }
    for($i = $offset, $x = 0, $count = (count($str_arr) - $offset); $i < $count, $x != $n; $i++){
        if($str_arr[$i] == $letter){
            $x++;
        }
    }
    return $i - 1;
}

echo nth_position('foobarbaz', 'a', 2); //7
echo nth_position('foobarbaz', 'b', 1, 4); //6
?>

If you would like to find all occurences of a needle inside a haystack you could use this function strposall($haystack,$needle);. It will return an array with all the strpos's.

<?php
/**
 * strposall
 * 
 * Find all occurrences of a needle in a haystack
 *
 * @param string $haystack
 * @param string $needle
 * @return array or false
 */
function strposall($haystack,$needle){
    
    $s=0;
    $i=0;
    
    while (is_integer($i)){
        
        $i = strpos($haystack,$needle,$s);
        
        if (is_integer($i)) { 
            $aStrPos[] = $i; 
            $s = $i+strlen($needle); 
        }
    }
    if (isset($aStrPos)) { 
        return $aStrPos; 
    } 
    else { 
        return false; 
    }
}
?>

here's a php implementation of stdc++ string class find_first_of using strpos.

<?php
function find_first_of($haystack, $needlesAsString, $offset=0)
{
  $max = strlen($needlesAsString);
  $index = strlen($haystack)+1;
  for($ii=0; $ii<$max;$ii++){
    $result = strpos($haystack,$needlesAsString[$ii], $offset);
    if( $result !== FALSE  && $result < $index)
      $index = $result;
  }
  return ( $index > strlen($haystack)? FALSE: $index);
}
?>

Example:
<?php
$test="Ralph: One of these days, Alice!!";
$look_for=":!,";   // punctuation marks

$ss = 0;
while( $answer=find_first_of($test,$look_for,$ss) ) {
  echo $answer . "\n";
  $ss = $answer+1;
 }
?>

This prints out:
5
24
31
32

Try this function to find the first position of needle before a given offset. 

For example:
<?php
$s = "This is a test a is This";
$offset = strpos($s, "test");

strnpos($s, "is", $offset);  // returns 17
strnpos($s, "is", -$offset); // returns 5

// Works just like strpos if $offset is positive.
// If $offset is negative, return the first position of needle
// before before $offset.
function strnpos($haystack, $needle, $offset=0)
{
    if ($offset>=0)
        $result=strpos($haystack, $needle, $offset);
    else
    {
        $offset=strlen($haystack)+$offset;
        $haystack=strrev($haystack);
        $needle=strrev($needle);
        $result=strpos($haystack, $needle, $offset);
        if ($result!==false)
        {
            $result+=strlen($needle);
            $result=strlen($haystack)-$result;
        }
    }
    return $result;
}

?>

Yay! I came up with a very useful function. This finds a beginning marker and an ending marker (the first after the beginning marker), and returns the contents between them. You specify an initial position in order to tell it where to start looking. You can use a while() or for() loop to get all occurence of a certain string within a string (for example, taking all hyperlinks in a string of HTML code)...

<?php
function get_middle($source, $beginning, $ending, $init_pos) {
    $beginning_pos = strpos($source, $beginning, $init_pos);
    $middle_pos = $beginning_pos + strlen($beginning);
    $ending_pos = strpos($source, $ending, $beginning_pos + 1);
    $middle = substr($source, $middle_pos, $ending_pos - $middle_pos);
    return $middle;
}
?>

For example, to find the URL of the very first hyperlink in an HTML string $data, use:

$first_url = get_middle($data, '<a href="', '"', 0);

It's done wonders for scraping HTML pages with certain tools on my website.

Code like this:
<?php
if (strpos('this is a test', 'is') !== false) {
    echo "found it";
}
?>

gets repetitive, is not very self-explanatory, and most people handle it incorrectly anyway. Make your life easier:

<?php
function str_contains($haystack, $needle, $ignoreCase = false) {
    if ($ignoreCase) {
        $haystack = strtolower($haystack);
        $needle   = strtolower($needle);
    }
    $needlePos = strpos($haystack, $needle);
    return ($needlePos === false ? false : ($needlePos+1));
}
?>

Then, you may do:
<?php
// simplest use
if (str_contains('this is a test', 'is')) {
    echo "Found it";
}

// when you need the position, as well whether it's present
$needlePos = str_contains('this is a test', 'is');
if ($needlePos) {
    echo 'Found it at position ' . ($needlePos-1);
}

// you may also ignore case
$needlePos = str_contains('this is a test', 'IS', true);
if ($needlePos) {
    echo 'Found it at position ' . ($needlePos-1);
}
?>

This is a function I wrote to find all occurrences of a string, using strpos recursively.

<?php
function strpos_recursive($haystack, $needle, $offset = 0, &$results = array()) {                
    $offset = strpos($haystack, $needle, $offset);
    if($offset === false) {
        return $results;            
    } else {
        $results[] = $offset;
        return strpos_recursive($haystack, $needle, ($offset + 1), $results);
    }
}
?>

This is how you use it:

<?php
$string = 'This is some string';
$search = 'a';
$found = strpos_recursive($string, $search);

if($found) {
    foreach($found as $pos) {
        echo 'Found "'.$search.'" in string "'.$string.'" at position <b>'.$pos.'</b><br />';
    }    
} else {
    echo '"'.$search.'" not found in "'.$string.'"';
}
?>

routine to return -1 if there is no match for strpos

<?php
//instr function to mimic vb instr fucntion
function InStr($haystack, $needle)
{
    $pos=strpos($haystack, $needle);
    if ($pos !== false)
    {
        return $pos;
    }
    else
    {
        return -1;
    }
}
?>

this function returns the text between 2 strings:

<?php
function get_between ($text, $s1, $s2) {
    $mid_url = "";
    $pos_s = strpos($text,$s1);
    $pos_e = strpos($text,$s2);
    for ( $i=$pos_s+strlen($s1) ; ( ( $i < ($pos_e)) && $i < strlen($text) ) ; $i++ ) {
        $mid_url .= $text[$i];
    }
    return $mid_url;
}
?>

if $s1 or $s2 are not found, $mid_url will be empty
to add an offset, simply compare $pos_s to the offset, and only let it continue if the offset is smaller then $pos_s.

if you want need a fast function to find the first occurrence of any ch element of an needle array this function might be of use: 
<?php
$eurl = strpos_needle_array($text, array('"'=>0,'\''=>0,'>'=>0, ' '=>0, "\n"=>0), $surl);

function strpos_needle_array(& $text, $needle_ary, $offset=0){    
    for($ch_pos=$offset;$ch_pos<strlen($text);$ch_pos++){
        if(isset($needle_ary[$text[$ch_pos]])){
            return $ch_pos;
        }
    }
    return false;
}
?>

Many people look for in_string which does not exist in PHP, so, here's the most efficient form of in_string() (that works in both PHP 4/5) that I can think of:
<?php
function in_string($needle, $haystack, $insensitive = 0) {
    if ($insensitive) {
        return (false !== stristr($haystack, $needle)) ? true : false;
    } else {
        return (false !== strpos($haystack, $needle))  ? true : false;
    }
}
?>

If you want to get all positions in an array, you can use this function. If the optional parameter count is especified, the function will put there the number of matches.

<?php
function strallpos($pajar, $aguja, $offset=0, &$count=null) {
  if ($offset > strlen($pajar)) trigger_error("strallpos(): Offset not contained in string.", E_USER_WARNING);
  $match = array();
  for ($count=0; (($pos = strpos($pajar, $aguja, $offset)) !== false); $count++) {
    $match[] = $pos;
    $offset = $pos + strlen($aguja);
  }
  return $match;
}
?>

when you want to know how much of substring occurrences, you'll use "substr_count".
But, retrieve their positions, will be harder.
So, you can do it by starting with the last occurrence :

function strpos_r($haystack, $needle)
{
    if(strlen($needle) > strlen($haystack))
        trigger_error(sprintf("%s: length of argument 2 must be <= argument 1", __FUNCTION__), E_USER_WARNING);

    $seeks = array();
    while($seek = strrpos($haystack, $needle))
    {
        array_push($seeks, $seek);
        $haystack = substr($haystack, 0, $seek);
    }
    return $seeks;
}

it will return an array of all occurrences a the substring in the string

Example : 

$test = "this is a test for testing a test function... blah blah";
var_dump(strpos_r($test, "test"));

// output 

array(3) {
  [0]=>
  int(29)
  [1]=>
  int(19)
  [2]=>
  int(10)
}

Paul-antoine
Malézieux.

I lost an hour before I noticed that strpos only returns FALSE as a boolean, never TRUE.. This means that

strpos() !== false 

is a different beast then:

strpos() === true

since the latter will never be true. After I found out, The warning in the documentation made a lot more sense.

strpos that accepts an array for $needle

<?php
// strpos that takes an array of values to match against a string
// note the stupid argument order (to match strpos)
function strpos_arr($haystack, $needle) {
    if(!is_array($needle)) $needle = array($needle);
    foreach($needle as $what) {
        if(($pos = strpos($haystack, $what))!==false) return $pos;
    }
    return false;
}
?>
----------------------------
http://www.show-ip.org

<?php
$my_array = array ('100,101', '200,201', '300,301');
$check_me_in = array ('100','200','300','400');
foreach ($check_me_in as $value_cmi){
    $is_in=FALSE; #asume that $check_me_in isn't in $my_array
    foreach ($my_array as $value_my){
        $pos = strpos($value_my, $value_cmi);
        if ($pos===0)
            $pos++;
        if ($pos==TRUE){
            $is_in=TRUE;
            $value_my2=$value_my;
            }
    }
    if ($is_in) echo "ID $value_cmi in \$check_me_in I found in value '$value_my2' \n";
}
?>

The above example will output
ID 100 in $check_me_in I found in value '100,101' 
ID 200 in $check_me_in I found in value '200,201' 
ID 300 in $check_me_in I found in value '300,301'

Function to get the string pos ($search), before the position ($pos) passed as parameter.

<?php

function strposReverse( $str, $search, $pos ){
        $str = strrev($str);
        $search = strrev($search);
        $pos = (strlen($str) - 1) - $pos;
        
        $posRev = strpos( $str, $search, $pos );
        return (strlen($str) - 1) - $posRev - (strlen($search) - 1);
    }
?>

A function that return the first occurance of a number in a string, if anyone needs it.

Translation/prevod:
Funkcija, ki vrača pozicijo prve številke v besedi, če jo kdo potrebuje.

<?php

    function firstNumPos($str) {
        $poses = array(); // will be storing positions of the numbers

        for($i = 0; $i < 10; ++$i) { // cycle through numbers
            if(($a = strpos($str, (string)$i)) !== false) {
                $poses[] = $a;    // append the position of
                                // the first occurance of the number
            }
        }
        if(isset($poses[0])) { // if array not empty
            sort($poses);        // sort to get the lowest one on the 'bottom'
            return $poses[0];    // and return it
        }
        return false; // otherwise return false

    } // firstNumPos()

?>

Hi! Don't you people miss the pretty comparison operator 'LIKE' from mySql in PHP??. 
I've made this funtion to emulate that method. It's for search a match string into another String 
using the '%' caracter just like you do un the LIKE syntax.
For example:

<?php
$mystring = "Hi, this is good!";
$searchthis = "%thi% goo%";

$resp = milike($mystring,$searchthis);

        
if ($resp){
   echo "milike = VERDADERO";
} else{
   echo "milike = FALSO";
}

?>
Will print:
milike = VERDADERO

and so on...

this is the function:

<?php
function milike($cadena,$busca){
    if($busca=="") return 1;
    
    $vi = split("%",$busca);
     $offset=0;
    for($n=0;$n<count($vi);$n++){
        if($vi[$n]== ""){
            if($vi[0]== ""){
                   $tieneini = 1;
            }
        } else {
            $newoff=strpos($cadena,$vi[$n],$offset);
            if($newoff!==false){
                if(!$tieneini){
                    if($offset!=$newoff){
                        return false;
                    }
                }
                if($n==count($vi)-1){
                    if($vi[$n] != substr($cadena,strlen($cadena)-strlen($vi[$n]), strlen($vi[$n]))){
                        return false;
                    }

                } else {
                    $offset = $newoff + strlen($vi[$n]);
                 }
            } else {
                return false;
            }
        }
    }
    return true;
}
?>

Good luck!

I wasn't aware of the !== operator, only the === for false. I was using this code on strpos:

<?php
while( ! ($start=@strpos($source,$startTag,$end)) === false) {
  // ...
}
?>

This gave a false if the string was found at position 0, which is weird. 

However using

<?php
while(($start=@strpos($source,$startTag,$end)) !== false) {
  // ...
}
?>

Gives no such error and seems to work correctly

str_replace evaluates its arguments exactly once.

for example:

<?php
$page = str_replace("##randompicture##", getrandompicture(), $page);
?>

will call getrandompicture() once, ie it will insert the same random picture for each occurrence of ##randompicture## :(

Here is my quick and dirty workaround:

<?php
function add_random_pictures($text) {

  while (($i = strpos($text, "##randompicture##")) !== false) {
    $text = substr_replace($text, getrandompicture(), $i, strlen("##randompicture##"));
  }
  return $text;

}

$page = add_random_pictures($page);
?>

Here's a somewhat more efficient way to truncate a string at the end of a word. This will end the string on the last dot or last space, whichever is closer to the cut off point. In some cases, a full stop may not be followed by a space eg when followed by a HTML tag.

<?php
    $shortstring = substr($originalstring, 0, 400);
    $lastdot = strrpos($shortstring, ".");
    $lastspace = strrpos($shortstring, " ");
    $shortstring = substr($shortstring, 0, ($lastdot > $lastspace? $lastdot : $lastspace));
?>

Obviously, if you only want to split on a space, you can simplify this:

<?php
    $shortstring = substr($originalstring, 0, 400);
    $shortstring = substr($shortstring, 0, strrpos($shortstring, " "));
?>

If you want to check for either IE6 or 7 individually.

<?php

function browserIE($version)
{
  if($version == 6 || $version == 7)
  {
    $browser = strpos($_SERVER['HTTP_USER_AGENT'], "MSIE ".$version.".0;");
           
    if($browser == true)
    {
      return true;
    }
    else
    {
      return false;
    }
  else
  {
    return false;
}

?>

here a little function for tag parsing

<?php
function parsing($tag,$string) {
        $start=strpos($string,"<" . $tag . ">" );
        $start=$start + strlen("<" . $tag . ">");
         $end=(strpos($string, "</" . $tag . ">"));
         $num=  ($end - $start);
         $valore=substr($string,$start,$num);
          return $valore;
}
?>

counting the occurrences of a substring, recursive-style instead of looping.

<?php
function countSubstrs($haystack, $needle)
{
    return (($p = strpos($haystack, $needle)) === false) ? 0 : (1 + countSubstrs(substr($haystack, $p+1), $needle));
}
?>

A simple function to find the number of occurances in a string within a string

<?php
function StringCount($searchstring, $findstring)
{
    return (strpos($searchstring, $findstring) === false ? 0 :  count(split($findstring, $searchstring)) - 1);
}
?>

When using GLOB_BRACE to find files on a local computer, note that including the drive lettername within the braces may cause the behavior to not work as expected:

<?php

$location = "{c:/foo/*.txt,c:/foo/bar/*.txt}"; // < will NOT work

$location = "c:{/foo/*.txt,/foo/bar/*.txt}"; // < works

$location = "c:/{foo/*.txt,foo/bar/*.txt}"; // < works

$location = "{/foo/*.txt,/foo/bar/*.txt}"; // < works

print_r(glob($location, GLOB_BRACE));

?>

Dan Brown and I had a discussion on the PHP list about the speed difference between the popular three string searching techniques. He wrote a simple timing test, and I adapted it further. The end result is that all three are very close and not even noticeable for sets < 1M. Although, technically strpos() is about twice as fast (as the docs allude to above). Here it is for your own amusement and testing purposes.

<?php
for ($i = 0; $i < 1000000; $i++ )
    $o[] =
sprintf('%04d-%02d-%02d',rand(0000,9999),rand(00,99),rand(00,99));
#print_r($o);
echo "array of ".number_format($i)."\n";
###################################################################
$now = microtime(true);
for($i=0;$i<count($o);$i++) {
       if(preg_match('/^[0]{4,}\-/U',$o[$i])) {
               //echo "Offset #".$i." matches: ".$o[$i].PHP_EOL;
       }
}
$rank['preg_match'] = (microtime(true) - $now);
###################################################################
$later = microtime(true);
for($i=0;$i<count($o);$i++) {
        if(substr($o[$i],0,4) == "0000") {
                //echo "Offset #".$i." matches: ".$o[$i].PHP_EOL;
        }
}
$rank['substr'] = (microtime(true) - $later);
###################################################################
$after = microtime(true);
for($i=0;$i<count($o);$i++) {
        if(strpos($o[$i], '0000') === 0) {
                //echo "Offset #".$i." matches: ".$o[$i].PHP_EOL;
        }
}
$rank['strpos'] = (microtime(true) - $after);
###################################################################
asort($rank);
print_r($rank);
?>

array of 10,000
Array
(
    [strpos] => 0.00766682624817
    [substr] => 0.0116670131683
    [preg_match] => 0.0124950408936
)

array of 100,000
Array
(
    [strpos] => 0.0817799568176
    [substr] => 0.120522975922
    [preg_match] => 0.125612974167
)

array of 1,000,000
Array
(
    [strpos] => 0.805890083313
    [substr] => 1.19799995422
    [preg_match] => 1.25615906715
)

I ran out of memory with more than 1M array elements.

A complete set of strn*pos functions that look for the nth occurrence of the needle in the haystack. I prefer this implementation of strnpos because it doesn't give visible warnings when supplied with a needle of length 0 (which is, admittedly, non-standard behavior).  Based on a version I [originally posted on 05-MAR-2010]; this new version conforms more to the semantics of strpos.

<?php

/**
 *  This function implements all the strn*pos functions, which return the $nth occurrence of $needle
 *  in $haystack, or false if it doesn't exist / when illegal parameters have been supplied.
 *
 *  @param  string  $haystack       the string to search in.
 *  @param  MIXED   $needle         the string or the ASCII value of the character to search for.
 *  @param  integer $nth            the number of the occurrence to look for.
 *  @param  integer $offset         the position in $haystack to start looking for $needle.
 *  @param  bool    $insensitive    should the function be case insensitive?
 *  @param  bool    $reverse        should the function work its way backwards in the haystack?
 *  @return MIXED   integer         either the position of the $nth occurrence of $needle in $haystack,
 *               or boolean         false if it can't be found.
 */
function strnripos_generic( $haystack, $needle, $nth, $offset, $insensitive, $reverse )
{
    //  If needle is not a string, it is converted to an integer and applied as the ordinal value of a character.
    if( ! is_string( $needle ) ) {
        $needle = chr( (int) $needle );
    }

    //  Are the supplied values valid / reasonable?
    $len = strlen( $needle );
    if( 1 > $nth || 0 === $len ) {
        return false;
    }

    if( $insensitive ) {
        $haystack = strtolower( $haystack );
        $needle   = strtolower( $needle   );
    }

    if( $reverse ) {
        $haystack = strrev( $haystack );
        $needle   = strrev( $needle   );
    }

    //  $offset is incremented in the call to strpos, so make sure that the first
    //  call starts at the right position by initially decreasing $offset by $len.
    $offset -= $len;
    do
    {
        $offset = strpos( $haystack, $needle, $offset + $len );
    } while( --$nth  && false !== $offset );

    return false === $offset || ! $reverse ? $offset : strlen( $haystack ) - $offset;
}

/**
 *  @see    strnripos_generic
 */
function strnpos( $haystack, $needle, $nth, $offset = 0 )
{
    return strnripos_generic( $haystack, $needle, $nth, $offset, false, false );
}

/**
 *  @see    strnripos_generic
 */
function strnipos( $haystack, $needle, $nth, $offset = 0 )
{
    return strnripos_generic( $haystack, $needle, $nth, $offset, true, false );
}

/**
 *  @see    strnripos_generic
 */
function strnrpos( $haystack, $needle, $nth, $offset = 0 )
{
    return strnripos_generic( $haystack, $needle, $nth, $offset, false, true );
}

/**
 *  @see    strnripos_generic
 */
function strnripos( $haystack, $needle, $nth, $offset = 0 )
{
    return strnripos_generic( $haystack, $needle, $nth, $offset, true, true );
}

$haystack = 'Dit is een HoTtentotTentenTentenToonstellingTest!';

echo strnpos  ( $haystack, 't', 5 ), ' === ', strnpos  ( $haystack, 116, 5 ), PHP_EOL;
echo strnipos ( $haystack, 't', 5 ), ' === ', strnipos ( $haystack, 116, 5 ), PHP_EOL;
echo strnrpos ( $haystack, 't', 5 ), ' === ', strnrpos ( $haystack, 116, 5 ), PHP_EOL;
echo strnripos( $haystack, 't', 5 ), ' === ', strnripos( $haystack, 116, 5 ), PHP_EOL;
echo PHP_EOL;
echo strnpos  ( $haystack, 'T', 5 ), ' === ', strnpos  ( $haystack,  84, 5 ), PHP_EOL;
echo strnipos ( $haystack, 'T', 5 ), ' === ', strnipos ( $haystack,  84, 5 ), PHP_EOL;
echo strnrpos ( $haystack, 'T', 5 ), ' === ', strnrpos ( $haystack,  84, 5 ), PHP_EOL;
echo strnripos( $haystack, 'T', 5 ), ' === ', strnripos( $haystack,  84, 5 ), PHP_EOL;
?>

The following function use to redirect to URL correctly if the URL have "http://" or "https://", or to relative URL on your site.

<?php
function forward($url = NULL){
    $root = "http://example.com/mydir/";
    
    if($url == NULL) // Go to homepage
        $url = $root;
    else {
        $pos = strpos($url, "http://");
        if ($pos === false) 
            $pos = strpos($url, "https://");
        
        if ($pos === false || $pos > 0) // Go to relative URL on your site
            $url = $root . $url;
    }
    
    header('Location:'.$url);    
}
?>

This function find position of first occurrence of any $needles in a string $haystack.
Return the position as an integer. If needles is not found, strposa() will return boolean  FALSE. 

<?php
function strposa($haystack ,$needles=array(),$offset=0){
    $chr = array();
    foreach($needles as $needle){
        $chr[] = strpos($haystack,$needle,$offset);
    }
    if(empty($chr)) return false;
    return min($chr);
}

$string = "This is my string, very simple.";

echo strposa($string,array(".",","," ")); // 2
echo strposa($string,array("T")); // 0
echo strposa($string,array("Q","W")); // false
?>