php pdf file to image

Why the file cannot be read? The permissions of the path pdf file have been set

<code>$PDF = './22.pdf';

$IM =new imagick();
   $IM->setResolution(120,120);
   $IM->setCompressionQuality(100);
   $IM->readImage($PDF);
   foreach($IM as $Key => $Var){
       $Var->setImageFormat('png');
       $Filename = './'.md5($Key.time()).'.png';
       if($Var->writeImage($Filename)==true){
           $Return[]= $Filename;
       }
   }
</code>

Error content: Fatal error: Uncaught exception 'ImagickException' with message 'Failed to read the file' in

Reply content:

Why the file cannot be read? The permissions of the path pdf file have been set

<code>$PDF = './22.pdf';

$IM =new imagick();
   $IM->setResolution(120,120);
   $IM->setCompressionQuality(100);
   $IM->readImage($PDF);
   foreach($IM as $Key => $Var){
       $Var->setImageFormat('png');
       $Filename = './'.md5($Key.time()).'.png';
       if($Var->writeImage($Filename)==true){
           $Return[]= $Filename;
       }
   }
</code>

Error content: Fatal error: Uncaught exception 'ImagickException' with message 'Failed to read the file' in

$PDF uses absolute path

<code>try {
    // read img
}  catch (ImagickException $e) {
    echo  exception;
}</code>