- array_column: documentation ( source)
- print_r: documentation ( source)
<?php
$details = array(
array('year' => '1990'),
array('year' => '1995'),
array('condition' => 'working'),
array('type' => 'bus'),
array('type' => 'car'),
array('type' => 'bike'),
);
$details = array_column($details, 'year');
print_r($details);