str_starts_with functionality, but the mentioned frameworks also contain str_ends_with functionality, often visible on the same web page
str_starts_with checks if a string begins with another string and returns a boolean value (true/false) whether it does.
str_ends_with checks if a string ends with another string and returns a boolean value (true/false) whether it does.
Typically this functionality is accomplished by using existing string functions such as substr, strpos/strrpos, strncmp, or substr_compare (often combined with strlen). These bespoke userland implementations have various downsides, discussed further below.
The str_starts_with and str_ends_with functionality is so commonly needed that many major PHP frameworks support it, including Symfony, Laravel, Yii, FuelPHP, and Phalcon 1).
Checking the start and end of strings is a very common task which should be easy. Accomplishing this task is not easy now and that is why many frameworks have chosen to include it. This is also why other high-level programming languages---as diverse as JavaScript, Java, Haskell, and Matlab---have implemented this functionality. Checking the start and end of a string should not be a task which requires pulling in a PHP framework or developing a potentially suboptimal (or worse, buggy) function in userland.
Ad hoc userland implementations of this functionality are less intuitive than dedicated functions (this is especially true for new PHP developers and developers who frequently switch between PHP and other languages---many of which include this functionality natively).
The implementation is also easy to get wrong (especially with the === comparison).
Additionally, there are performance issues with many userland implementations.
Note: some implementations add “$needle === "" || ” and/or “strlen($needle) <= strlen($haystack) && ” guards to handle empty needle values and/or avoid warnings.
This is memory inefficient because it requires an unnecessary copy of part of the haystack.
strpos($haystack, $needle) === 0
This is potentially CPU inefficient because it will unnecessarily search along the whole haystack if it doesn't find the needle.
strncmp($haystack, $needle, strlen($needle)) === 0 // generic strncmp($subject, "prefix", 6) === 0 // ad hoc
This is efficient but requires providing the needle length as a separate argument, which is either verbose (repeat “$needle”) or error prone (hard-coded number).
This is memory inefficient (see above).
This is doubly inefficient because it requires reversing both the haystack and the needle as well as applying strpos (see above).
This is verbose and also potentially CPU inefficient.
substr_compare($haystack, $needle, -strlen($needle)) === 0 // generic substr_compare($subject, "suffix", -6) === 0 // ad hoc
This is efficient but either verbose or error prone (see strncmp above).
Add two new basic functions: str_starts_with and str_ends_with:
str_starts_with ( string $haystack , string $needle ) : bool str_ends_with ( string $haystack , string $needle ) : bool
str_starts_with() checks if $haystack begins with $needle. If $needle is longer than $haystack, it returns false; else, it compares each character in $needle with the corresponding character in $haystack (aligning both strings at their start), returning false if it encounters a mismatch, and true otherwise.
str_ends_with() does the same thing but aligning both strings at their end.
Examples below:
$str = "beginningMiddleEnd"; if (str_starts_with($str, "beg")) echo "printed\n"; if (str_starts_with($str, "Beg")) echo "not printed\n"; if (str_ends_with($str, "End")) echo "printed\n"; if (str_ends_with($str, "end")) echo "not printed\n"; // empty strings: if (str_starts_with("a", "")) echo "printed\n"; if (str_starts_with("", "")) echo "printed\n"; if (str_starts_with("", "a")) echo "not printed\n"; if (str_ends_with("a", "")) echo "printed\n"; if (str_ends_with("", "")) echo "printed\n"; if (str_ends_with("", "a")) echo "not printed\n";
Note: the behavior concerning empty strings is in accordance with what is described in the accepted str_contains RFC. This behavior is also the same as is common with other languages, including Java and Python.
This could break functions existing in userland with the same names. But see the corresponding section in the str_contains RFC for a discussion illustrating how this concern may be mitigated and why it does not justify the rejection of this RFC.
PHP 8
Voting closes 2020-05-04
After the project is implemented, this section should contain
str_starts_with functionality, but the mentioned frameworks also contain str_ends_with functionality, often visible on the same web page