จากโค้ดด้านล่างมีทางทำให้สั้นและเข้าใจง่ายกว่านี้มั้ยครับ

$a = array("121/54-1312-060-03-1(30)", "121/54-1312-060-03-2(30)", "121/54-1312-060-03-3(30)", "121/54-1312-060-03-4(30)");
$result = array();
foreach($a as $key => $value){
        $b = explode("-", $a[$key]);
        $c = explode("(", $b[4]);
        $result[$key] = $c[0];
}

$x = "121/54-1312-060-03-";
$y = "(30)";

$cn = count($result);

echo $x;
foreach($result as $key => $value){
    if($cn == $result[$key]){
             echo $value;
    }else{
            echo $value.",";
    }
}
echo $y;