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).'" /> ';
}
}
?>