URL image validation

I'm trying to write a method to validate an image from a URL. The method will accept an array of image URL. The image should be validated by its type, size and dimensions. Right now, I'm able to implement it but I'm having a problem on how long it takes to finish the validation.

Is there any alternative on my current approach that might speed up the validation process?

public function validate_attachment($attachment){
    $image = "";
    if(strpos($attachment,",") !== false){
      $image = explode(",", $attachment);
    }else{
      $image = array($attachment);
    }

    foreach ($image as $url) {

      $ch = curl_init($url);
      curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
      curl_exec($ch);

      switch (curl_getinfo($ch, CURLINFO_CONTENT_TYPE)) { //validate file type

        case 'image/png' :
        case 'image/jpg' :
        case 'image/jpeg':
        case 'image/gif' :
          echo curl_getinfo($ch, CURLINFO_CONTENT_TYPE) ."<br />";
          $type = true;
          $filesize =  curl_getinfo($ch, CURLINFO_SIZE_DOWNLOAD)/1024 ."<br/>"; // validate image size
          echo $filesize;
          if($filesize <= 70){
            echo $filesize;
            list($width, $height) = getimagesize(curl_getinfo($ch, CURLINFO_EFFECTIVE_URL)); // validate image dimensions
            if($width <= 800 && $height <= 600){
              echo "width: " . $width . "<br />";
              echo "height: " .  $height ."<br/>";
            }else{
              echo "Image too large";
            }
            curl_close($ch);

          }else{
            echo "file size should be below 70kb";
          }
          break;
        default:
          echo "Invalid file type.";
          break;
      }
    }
  }