Isn't it super trivial given the way substr works in PHP?

startswith:
substr($haystack,0,strlen($prefix)) == $prefix

endswith:
substr($haystack,-strlen($suffix)) == $suffix

Usually we add things to core that can't be done with a single trivial 
call in PHP.  The only thing you save is the strlen call, and you can 
hardcode that to avoid it.

rasmus, this is right in nearly all cases, but here are some corner cases where your code fails:

startswith('', '0')
should be false, but your code gives true
reason: substr('', 0, 1)  is  false
        false == '0'  is  true

if you try to fix this by replacing == with ===, another corner case will fail:

startswith('', '')
should be true, but will be false
reason: substr('', 0, 0)  is  false
        false === ''  is  false

this seems to work in all cases:

function str_startswith($string, $prefix) {
	if (strlen($string) < strlen($prefix))
		return false;
	return substr($string, 0, strlen($prefix)) == $prefix;
}


similar for endswith:

endswith('', '0')  should be false, but is true
endswith('test', '')  should be true, but is false

this seems to work in all cases:

function str_endswith($string, $suffix) {
	$suffixLength = strlen($suffix);
	if ($suffixLength == 0)
		return true;
	if (strlen($string) < $suffixLength)
		return false;
	return substr($string, -$suffixLength) == $suffix;
}

Possible problems with the above corner cases are not the main reasons why I requested these functions.  Even if I know this corner cases will not occur in my application I'll prefer str_startswith($s, $p) to substr($s, 0, strlen($p)) == $p because it's shorter and easier to read.

This functionality is so often needed and when you need it, you have do use the substr expression or define you own str_startswith function.  So why not adding it to the PHP core since it's such a basic thing...

I would also like to see this. It's very handy for string checking. Both Python 
and C# have such a method. (accompanied by Python's in, it's very handy) For 
brevity I'd prefer startswith() and endswith(), however.

I think I'll write a patch :)

Please?

http://stackoverflow.com/questions/834303/php-startswith-and-endswith-functions

Requests for these functions come up again and again.
Case insensitive variants might be useful too.

olafvdspek: Oh, lots of us would like it, but it apparently adds unnecessary bloat 
so we obviously can't have it, even if it would help code readability and mean 
people would spend less time reinventing the wheel.

FTR: there is a respective RFC currently under discussion, see
<https://wiki.php.net/rfc/add_str_begin_and_end_functions>.

This was added to PHP 8.0 via https://wiki.php.net/rfc/add_str_starts_with_and_ends_with_functions.