如何检查缓存的图像是否与url图像具有相同的宽度和高度？

Question

I am writing a script where I am just resizing images from the requested image url and caching them. I am also giving width & height as optional params for the request. I am caching the images by their filenames & I want to cover one use case when user requests the same image with different width or height.

Since I am using Codeigniter's image resizing library, the filenames are appended with _thumb. That's how I am storing the images.

What should I do in that case? One solution would be to check the md5 hash of the resized image and cached image.

Here's what I am thinking to do:

            $ch = curl_init($url); //initialize cURL

            curl_setopt($ch, CURLOPT_HEADER, 0); 
            curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1); 
            curl_setopt($ch, CURLOPT_BINARYTRANSFER, 1); 
            $dataToWrite = curl_exec($ch); //Execute the given cURL session. 

            curl_close ($ch); //close the given cURL session
            $fp = fopen($dirPath.$filename,'w');
            fwrite($fp, $dataToWrite); 
            fclose($fp);

Finally,

           if (md5_file($dirPath.$filename) == md5_file($dirPath.$resizedImage){
                serveimagefromcache() & deletethedownloadedfile();
           } else {
               resizetheimage() && serveit(); 
           }

I am concerned about the performance as well, I would appreciate any other suggestions.

Answer 1

Even though @arkascha's suggestion was quite good but saving the file as filename hash is much more better.

With this,

$ext   = pathinfo($filename, PATHINFO_EXTENSION);    
$filehash = sha1($filename.$width.$height);
$filename = $filehash.".".$ext

you can prevent the issue that I was having.