php合并排序

$a = array(1,5,12,16);
$b = array(2,3,15,19,25);
$c = array(); 
$ak = $bk = 0;
$countA = count($a); 
$countB = count($b);
$countAB = $countA + $countB;

for($i=0; $i<$countAB; $i++) {
    if($ak<$countA && $bk<$countB) {
        if($a[$ak] < $b[$bk] ) {
            $c[$i] = $a[$ak]; 
            unset($a[$ak]);
            $ak++;
        } else {
            $c[$i] = $b[$bk]; 
            unset($b[$bk]);
            $bk++;
        }
    }
}

$end = $a ? $a : $b;
foreach($end as $v) {
    array_push($c, $v);
}

echo ‘<pre>‘;print_r($c);die;