September 29th, 2006
Find a string within a string in PHP
The PHP function strrpos is great for finding the positiong of a specific character within a string. But that's exactly the problem: that it really only can search for a character. So, digging around the PHP manual, I was able to drum up this handy function, which enables you to search for entire strings, rather than individual characters. This is a recursive function, and is quite efficient.
<?php
//Find last occurance of needle in haystack
function str_rpos($haystack, $needle, $start = 0){
$tempPos = strpos($haystack, $needle, $start);
if($tempPos === false){
if($start == 0){
//Needle not in string at all
return false;
}else{
//No more occurances found
return $start - strlen($needle);
}
}else{
//Find the next occurance
return str_rpos($haystack, $needle, $tempPos + strlen($needle));
}
}
?>
//Find last occurance of needle in haystack
function str_rpos($haystack, $needle, $start = 0){
$tempPos = strpos($haystack, $needle, $start);
if($tempPos === false){
if($start == 0){
//Needle not in string at all
return false;
}else{
//No more occurances found
return $start - strlen($needle);
}
}else{
//Find the next occurance
return str_rpos($haystack, $needle, $tempPos + strlen($needle));
}
}
?>
