- array_column: documentation ( source)
- print_r: documentation ( source)
<?php
$a = array(
array(
array(
'plm1' => "1",
'plm2' => "2",
'plm3' => "3",
),
'plm1' => "4",
'plm3' => "5",
'plm4' => "6",
),
array(
'plm1' => "2",
'plm3' => "3",
'plm4' => "4",
),
);
print_r(array_column($a, "plm1"));