Get specific element from each sub array

Question

I have a common pattern which Im sure there must be a built-in array function in PHP to handle but just can\'t see it.

I have multiple arrays such as the following:<

Answer 1

Before PHP 5.5, this would be the most efficient solution:

$key = 'key1';

$output = array_map(function($item) use ($key) {
    return $item[$key];
}, $testArray);

As of PHP 5.5, there is now an array_column function for this (see COil's answer).