print_r($array);
Array ( [0] => A [1] => B [2] => A [3] => O )
unset($array[2]); print_r($array);
Array ( [0] => A [1] => B [3] => O )
$array = array_values($array); print_r($array);
Array ( [0] => A [1] => B [2] => O )