php imagick库处理pdf有关问题

function pdf2png($PDF,$toPath,$page){   
if(!extension_loaded('imagick')){
echo "imagick";
return false;   
}   
if(!file_exists($PDF)){
echo "noexists";
return false;   
}
$IM = new imagick();   

$IM->setResolution(1000,2000);   

$IM->setCompressionQuality(100);   

$IM->readImage($PDF."[".$page."]");

foreach ($IM as $Key => $Var){
$Var->setImageFormat('png');       
$Filename = $toPath.time().'_'.$Key.'.png';       
if($Var->writeImage($Filename) == true){           
$Return[] = $Filename;       
}
}
return $Return;
}