- array_column: documentation ( source)
- var_export: documentation ( source)
- array_values: documentation ( source)
<?php
$array = [
['key' => 1],
['key' => 2],
['key' => 3],
['key' => 1],
['key' => 2],
['key' => 3],
['key' => 4],
['key' => 5],
['key' => 6]
];
var_export(array_values(array_column($array, 'key', 'key')));