<?php

$arr = Array(16, 17, 18, 23, 7, 6, 14, 22);
$split_by = array_search(23, $arr);

if ($split_by) {
    $first = array_slice($arr, 0, $split_by);
    $second = array_slice($arr, $split_by);
    
    var_dump($first, $second);
}