Care must be taken when using the spaceship operator with arrays that do not have the same keys:
- Contrary to the notes above ("Example #2 Transcription of standard array comparison"), it does *not* return null if the left-hand array contains a key that the right-hand array does not.
- Because of this, the result depends on the order you do the comparison in.
For example:
<?php
$a = ['a' => 1, 'b' => 2, 'c' => 3, 'e' => 4];
$b = ['a' => 1, 'b' => 2, 'd' => 3, 'e' => 4];
var_dump($a <=> $b); var_dump($b <=> $a); ?>
