php多張圖片拼接成一張圖片

<?php
$imgs    = array();
$imgs[0] = 'imgs/1.jpg';
$imgs[1] = 'imgs/2.jpg';
$imgs[2] = 'imgs/3.jpg';
$imgs[3] = 'imgs/4.jpg';
$target  = 'emp.jpg'; //背景圖片

$target_img = Imagecreatefromjpeg($target);
$source = array();
foreach ($imgs as $k => $v) {
    $source[$k]['source'] = Imagecreatefromjpeg($v);

$source[$k]['size'] = getimagesize($v);


}
//imagecopy ($target_img,$source[0]['source'],2,2,0,0,$source[0]['size'][0],$source[0]['size'][1]);
//imagecopy ($target_img,$source[1]['source'],250,2,0,0,$source[1]['size'][0],$source[1]['size'][1]);
$num1 = 0;
$num  = 1;
$tmp  = 2;
$tmpy = 2; //圖片之間的間距
for ($i = 0; $i < 4; $i++) {
    imagecopy($target_img, $source[$i]['source'], $tmp, $tmpy, 0, 0, $source[$i]['size'][0], $source[$i]['size'][1]);

$tmp = $tmp + $source[$i]['size'][0];
$tmp = $tmp + 5;
if ($i == $num) {
    $tmpy = $tmpy + $source[$i]['size'][1];
    $tmpy = $tmpy + 5;
    $tmp  = 2;
    $num  = $num + 3;
}

}
Imagejpeg($target_img, 'pin.jpg');
?>
<img src="pin.jpg"></pre>