PHP RFC: Create "split" as an alias to "explode"

Version: 1.2
Date: 2025-08-17
Author: Vinicius Dias, carlosv775@gmail.com
Status: Declined
Implementation: https://github.com/php/php-src/pull/19490

Introduction

PHP has the concept of alias functions, where a function can have more than one name. Here are some examples of aliases:

Alias	Function
`sizeof`	`count`
`chop`	`rtrim`
`die`	`exit`
`join`	`implode`

In several languages, the inverse operation of join is split, but in PHP, we call it explode (the inverse of implode).

This RFC proposes a new alias to the explode function called split.

<?php
 
// The following lines would be equivalent
$array = explode(' ', 'String with spaces');
$array = split(' ', 'String with spaces');

Proposal

Several languages use the word split for the function that separates a string into an array using a separator, and join for its inverse operation (joining an array into a string). PHP functions for those purposes are, respectively, explode and implode.

That difference from the majority of languages was mitigated with a join alias to the implode function, so a person coming to PHP from a different language has one less “strange” thing to get used to, but there is no split alias to explode.

In older versions of PHP, there was a function named split which was part of the extension ereg and could be used to split a string into an array by a regular expression pattern. The ext/ereg was deprecated in PHP 5.3 and removed in PHP 7.0. Since then, the split function name has not been used and is available.

This RFC has one simple purpose: creating a new function alias called split that will execute the exact same code as explode. Neither parameters nor any behavior will change with this RFC. It will only make the following possible:

<?php
 
$str = 'one|two|three|four';
 
print_r(split('|', $str));
 
print_r(split('|', $str, 2));

Which would result in the following output:

Array
(
    [0] => one
    [1] => two
    [2] => three
    [3] => four
)

Array
(
    [0] => one
    [1] => two|three|four
)

Why add a new alias?

Some people might question how useful a new alias would be, and that is a valid concern.

Whenever we developers learn a new language, we find similarities and differences from the programming languages we already know. When something is similar, we tend to assimilate it faster and feel more comfortable with the feature in question. Whenever something is very different from what we are used to, it adds some cognitive load and can make the process more challenging.

As it was mentioned previously (and added to the references), multiple other programming languages use split as the word for this functionality, so having it in PHP would just make people coming from those languages a little bit more comfortable.

As Paul Dragoonis mentioned:

Making it a smoother transition for JS devs to hop back on the modern PHP train is in all our shared interest in terms of user base, and split() would help this.

This applies to other languages too.

In the references, I am adding a small number of “complaints” in social media where users mention that split would be an interesting alias.

Caveats and Arguments against

Dislike for aliases

Some people might be against the idea of adding aliases to PHP, even though we already have that concept and multiple aliases are available. If we don't want to keep using aliases, we should create a separate RFC to remove the existing ones and prevent new ones from being created. Since this is not the case, an alias is a valid part of the language and a new one is a valid approach.

Confusion with other functions

str_split

PHP has a ''str_split'' function that performs a different task. It converts a string into an array, but doesn't use a separator. It separates the string by a chunk size, which is passed as the second parameter.

ext/ereg split

As mentioned in the Proposal section, ext/ereg had a split function, but it was deprecated in PHP 5.3 and removed in PHP 7.0. A person migrating from PHP 5.3 to PHP 8.6 would be surprised by a new behavior of the split function, but that is a scenario highly unlikely to happen.

mb_split

The mb_split function has a similar behavior to the old ext/ereg split, but it depends on Oniguruma, which is not maintained anymore since 2025-04-24 and there is an RFC to deprecate (and remove) it: PHP RFC: Oniguruma maintenance was end

Backward Incompatible Changes

With this new alias, \split() would no longer be available to userland.

Proposed PHP Version(s)

8.6

RFC Impact

To the Ecosystem

Searching for the usage of split on GitHub, most of the occurances are either for repositories from over 10+ years without any activity or with the function being used in a way that would not be a BC change (or both).

Examples of cases where the behavior would not change:

https://github.com/cloudfour/image-breakpoints/blob/master/bps.php#L97C1-L103C64

<?php
 
// ...
if ($vars['upper'] === FALSE) {
  $vars['upper'] = $source_width . 'x' . $source_height;
}
 
// Limit the upper value to the size of the source image
list($upper_width, $upper_height) = split("x", $vars['upper']);

https://github.com/fruminator/openstreetblock/blob/master/osb.php#L26:

<?php
 
// ...
$ll = split(",", $ll);

https://github.com/bandoche/pyLine/blob/master/gd2.php#L178:

<?php
 
// ...
$rsa_keys = split(',', $rsa_key);

To Existing Extensions

None

To SAPIs