An array that represents a possible record set returned from a database
<?php
// An array that represents a possible record set returned from a database
$a = array(
  array(
    'id' => 5698,
    'first_name' => 'Peter',
    'last_name' => 'Griffin',
  ),
  array(
    'id' => 4767,
    'first_name' => 'Ben',
    'last_name' => 'Smith',
  ),
  array(
    'id' => 3809,
    'first_name' => 'Joe',
    'last_name' => 'Doe',
  )
);
$last_names = array_column($a, 'last_name');
echo "<pre>";
print_r($last_names);
echo "<pre>";
// output
Array
(
    [0] => Griffin
    [1] => Smith
    [2] => Doe
)
?>