php实现图片上传并利用ImageMagick生成缩略图

<?php
// location to upload main image:
$maindir = $_server['document_root'].'/images/l/';
// location to create the thumb image:
$smaldir = $_server['document_root'].'/images/s/';
// command to use:
$command = '/usr/bin/convert';
// thumbnail width:
$size = 210;
// make sure we have an image:
if(isset($_post['submit'])){
if(getimagesize($_files['photo']['tmp_name'])){
$name = $_files['photo']['name'];
$uploadfile = $maindir . $name;
move_uploaded_file($_files['photo']['tmp_name'], $uploadfile);
$lrgimg = $maindir . $name;
$smlimg = $smaldir . $name;
$imagemagick = $command . " '". $lrgimg . "' -resize '$size' '" . $smlimg . "'";
shell_exec($imagemagick);
}
header("location: /test.php");
exit;
}else{
?>
<form action=" <?php echo $_server['php_self']; ?> " method="post" enctype="multipart/form-data">
<p><input type="file" name="photo" /></p>
<p><input type="submit" value="upload!" name="submit" /></p>
</form>
<?php
foreach(glob($smaldir.'*') as $img){
echo ' <img src="'.str_replace($_server['document_root'], '',$img).'" /> ';
}
}
?>