The strpos() function behaves identically in PHP 8.4 and PHP 8.5. There are no version specific changes or deprecations for this function in either release. The most recent behavioral changes were in PHP 8.0.0, which are already well established.
Function
strpos() finds the numeric position of the first occurrence of a substring (needle) in a string (haystack). It is case-sensitive and binary safe.
Signature:
strpos(string $haystack, string $needle, int $offset = 0): int|false
Key Behavior:
→Return Value: Returns the position as an integer (starting at 0), or false if the needle is not found.
→Strict Comparison: You must use === or !== to check the result. A simple == check will fail if the substring is found at position 0, because 0 loosely equals false.
→Offset: The optional $offset parameter tells PHP where to start searching. A negative offset starts counting from the end of the string.
Examples
1. Basic Usage with Strict Comparison
<?php
$mystring = abc ;
$findme = a ;
$pos = strpos($mystring, $findme);// Use === to avoid confusion with position 0 evaluating to false
if ($pos === false) {
echo "The string $findme was not found in the string $mystring ";
} else {
echo "The string $findme was found in the string $mystring ";
echo " and exists at position $pos";
}
// Outputs: The string a was found in the string abc and exists at position 0
?>
This is the most critical pattern to remember. Without ===, a match at the very start of a string would be treated as a failure.
2. Using an Offset
<?php
$newstring = abcdef abcdef ;
// Search for a , but start looking after the first character
$pos = strpos($newstring, a , 1);
echo $pos; // Outputs: 7
?>
The search skips the a at position 0 and finds the next one at position 7.
3. Modern Alternative (PHP 8+) If you only need to check whether a string contains another string (and don not need the position), use str_contains() instead. It returns a simple boolean and avoids the === false pitfall entirely.
<?php
if (str_contains( How are you? , are )) {
echo notrue ;
}
?>