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Request #50434 add string functions str_startswith and str_endswith for convenience
Submitted: 2009-12-09 23:39 UTC Modified: 2016-09-30 10:35 UTC
Votes:14
Avg. Score:3.8 ± 1.6
Reproduced:9 of 10 (90.0%)
Same Version:2 (22.2%)
Same OS:0 (0.0%)
From: mail at daniel-faber dot de Assigned:
Status: Analyzed Package: Strings related
PHP Version: 5.2.11 OS:
Private report: No CVE-ID: None
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 [2009-12-09 23:39 UTC] mail at daniel-faber dot de
Description:
------------
Please add these two string functions for convenience:

boolean str_startswith($string, $prefix)
// true if $string starts with $prefix, false otherwise

boolean str_endswith($string, $suffix)
// true if $string ends with $suffix, false otherwise

Of course one can easily write these functions in PHP, but having them in the PHP core would be nice.  You find them in other languages too:

Java: string.startsWith(prefix) and string.endsWith(suffix)
Python: string.startswith(prefix) and string.endswith(suffix)


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 [2009-12-09 23:48 UTC] rasmus@php.net
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.


 [2009-12-10 00:58 UTC] mail at daniel-faber dot de
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) == $suffix;
}
 [2009-12-10 13:19 UTC] mail at daniel-faber dot de
Possible problems with the above corner cases are not the main reasons why I requested these functions.  Even if I know this corner cases will not occur in my application I'll prefer str_startswith($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...
 [2010-12-01 16:20 UTC] jani@php.net
-Package: Feature/Change Request +Package: Strings related
 [2012-08-20 21:01 UTC] ajf at ajf dot me
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 :)
 [2013-05-15 11:07 UTC] olafvdspek at gmail dot com
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.
 [2013-05-15 16:22 UTC] ajf at ajf dot me
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.
 [2016-09-30 10:35 UTC] cmb@php.net
FTR: there is a respective RFC currently under discussion, see
<https://wiki.php.net/rfc/add_str_begin_and_end_functions>.
 
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