How to check if string contains substring in PHP?

Use strpos($string, $search) !== false. Returns position if found, false if not found.

Is strpos() case-sensitive?

Yes, strpos() is case-sensitive. Use stripos() for case-insensitive search.

strpos() returns 0 if found at start, which is falsy. Use !== false for strict comparison.

String Function PHP 4+

The strpos() function finds the position of the first occurrence of a substring in a string.

strpos(string $haystack, string $needle, int $offset = 0): int|false

Parameter	Type	Description
`$haystack`	string	The string to search in
`$needle`	string	The substring to find
`$offset`	int	Start search from this position (optional)

Returns the position (0-indexed) of the first occurrence, or false if not found.

Output

Click Run to execute your code

<?php
$str = "Hello World";
if (strpos($str, "World") !== false) {
    echo "Found!";
}
?>

<?php
$str = "Hello World";
echo stripos($str, "world"); // 6 (case-insensitive)
?>

Important: Always use === false or !== false when checking the result, because position 0 is valid but falsy.