php internal server error when checking for files on different domain

Question

using the solution provided on this Get file contents of a domain in another domain in the same server I am getting list of the folders present in domain1.com.There are more than 5000 folders. Each folder contains detail folder with different images .Now i want to check for all the images in detail folder .The below code updates few records but it gives me 500 Internal Server Error after sometime.

$url_img = 'http://domain1.com/prod_images/' . $foldername . '/' . 'detail/' . $image_path1;
$url=getimagesize($url_img);

if(!is_array($url))
{
    upd_sql = "Update prod_images set image_exist_flag='No' where style='$style1' and image_path = '$image_path1'";
    $conn->query($upd_sql);

}else{
    $upd_sql = "Update prod_images set image_exist_flag='Yes' where style='$style1' and image_path = '$image_path1'";
   $conn->query($upd_sql);

}