Unpacking inside arrays using spread operator in PHP
Pre PHP 7.4, if you want to merge two arrays, you would need to use methods like array_merge. Take this for example.
<?php // Pre PHP 7.4 $array = ['foo', 'bar']; $result = array_merge($array, ['baz']); print_r($result); // Array( => baz  => foo  => bar)
But from PHP 7.4, you can achieve above using following syntax:
<?php // From PHP 7.4 $array = ['foo', 'bar']; $result = ['baz', ...$array]; print_r($result); // Array( => baz  => foo  => bar)
You can even unpack multiple arrays into a single array which is not possible using methods such as
array_merge as the method like these can only take two arrays at a time.
You may like: Array unpacking with string keys coming in PHP 8.1
There’s one issue however with this implementation. And that is you can not unpack the associative arrays. Doing so will throw a fatal error.
So, if we modify the above example into using an associative array and run it…
<?php $array = ['foo' => 'pikachu', 'bar' => 'pokemon']; $result = ['baz', ...$array]; print_r($result);
…It will halt the script with the following fatal error.
<b>Fatal error</b>: Uncaught Error: Cannot unpack array with string keys in [...][...]:6
So, you would need to keep this in mind while using the spread operator. At least, for now. But I’m pretty sure a workaround for this issue will be there in the upcoming versions of PHP.