What's the most efficient test of whether a PHP string ends with another string?

The standard PHP way to test whether a string $str ends with a substring $test is:

$endsWith = substr( $str, -strlen( $test ) ) == $test

Is this the fastest way?

Answer

What Assaf said is correct. There is a built in function in PHP to do exactly that.

substr_compare($str, $test, strlen($str)-strlen($test), strlen($test)) === 0;

If $test is longer than $str PHP will give a warning, so you need to check for that first.

function endswith($string, $test) {
    $strlen = strlen($string);
    $testlen = strlen($test);

    if ($testlen > $strlen) return false;
    return substr_compare($string, $test, $strlen - $testlen, $testlen) === 0;
}