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

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;
}

This method is a tiny bit more memory-expensive, but it is faster:

stripos(strrev($haystack), $reversed_needle) === 0;

This is best when you know exactly what the needle is, so you can hard-code it reversed. If you reverse the needle programmatically, it becomes slower than the earlier method.

Edit (12 years later): LOL, this is a super-old answer that I wrote when I didn't know what I was actually talking about. I'd like the think I've grown since then. @DavidHarkness is right, it is not very efficient in the negative case. Probably much faster to just iterate in reverse and bail early if you really need as much perf as possible. Also, php probably has better ways to do this now. Honestly, I haven't written php in nearly a decade, so I'll leave it up to others now.

It depends on which sort of efficiency you care about.

Your version uses more memory due to the extra copy from the use of substr.

An alternative version might search the original string for the last occurrence of the substring without making a copy, but would probably be slower due to more testing.

Probably the most efficient way is to do loop char-by-char from the -sterlen(test) position till the end of the string and compare. That's the minimal amount of comparisons you can hope to do and there's hardly any extra memory used.

In PHP 8:

str_ends_with('haystack', 'stack'); // true
str_ends_with('haystack', 'K'); // false

and also:

str_starts_with('haystack', 'hay'); // true

PHP RFC: Add str_starts_with(), str_ends_with() and related functions

Another way would be to use the strrpos function:

strrpos($str, $test) == strlen($str) - strlen($test)

But that’s not faster.

easiest way to check it via regular expression

for example to check if the mail given is gmail:

echo (preg_match("/@gmail\.com$/","example-email@gmail.com"))?'true':'false';

I'm thinking the reverse functions like strrchr() would help you match the end of the string the fastest.

for single-char needle:

if (@strrev($haystack)[0] == $needle) {
   // yes, it ends...
}