Online PHP editor | output for Qj98N

<?php $arr = [ 0 => [ "SERIAL" => "qwerty", "BRANCH" => "TEST1" ], 1 => [ "SERIAL" => "qwer", "BRANCH" => "TEST1" ], 2 => [ // RETURN THIS AS ERROR AS THE BRANCH "TEST1" has already "qwerty" serial "SERIAL" => "qwerty", "BRANCH" => "TEST2" ], 3 => [ "SERIAL" => "qwerty", "BRANCH" => "TEST1" ], 4 => [ // RETURN THIS AS ERROR AS THE BRANCH "TEST1" has already "qwerty" serial "SERIAL" => "qwerty", "BRANCH" => "TEST3" ], ]; foreach($arr as $sub){ $result[$sub['SERIAL']][] = $sub['BRANCH']; } foreach($result as $branches){ $unique = array_unique($branches); if(count($unique) >1){ var_dump("ERROR:", array_slice($unique,1)); } }