send data from embedded game through PHP?

Hi, I'm looking to upload and embed my game to an online website, and have found an online host simmer.io to upload my game. However I want to send the game data through a PHP script to write the game data to a local file.

I followed this tutorial from Holistic3D on reading and writing to a text file from unity webGL (https://www.youtube.com/watch?v=4OZqY1Ukj8I) and got this piece of code that supposedly talks to the PHP server.

     public void saveScores()
     {
         StartCoroutine(sendTextToFile());
         SceneManager.LoadScene("Close prompt");
     }
 
 
 
     IEnumerator sendTextToFile()
     { bool successful = true;
         WWWForm form = new WWWForm();
         form.AddField("Name", participantID);
         form.AddField("MC_attempts", MC_attempts);
         form.AddField("MC_time_taken", MC_time);
         form.AddField("Ped_attempts", Ped_attempts);
         form.AddField("Ped_time_taken", Ped_time);
         form.AddField("Level_order", levelOrder);
         WWW www = new WWW("https://simmer.io/@Pancy/Pelmanism/sendfromunity.php", form);   //line51
 
         yield return www;
         if (www.error != null)
         {
             successful = false;
         }
         else
         {
             Debug.Log(www.text);
             successful = true;
         }
     }

and then I've got this PHP code that should write the data to a text file:

 <?php
 
     $Name =$_POST["Name"];
     $MC_attempts = $_POST["MC_attempts"];
     $MC_time = $_POST["MC_time_taken"];
     $Ped_attempts = $_POST["Ped_attempts"];
     $Ped_time = $_POST["Ped_time_taken"];
     $levelOrder = $_POST["Level_order"];
 
 
 
     if ($Name != "")
     {
         echo("Message successfully sent");
         echo("Field 1: " . $Name);
         echo("Field 6: " . $levelOrder);
         $file = fopen("webgl_data.txt", "a");
         fwrite($file, $Name." ".$MC_attempts." ".$MC_time." ".$Ped_attempts." ".$Ped_time." ".$levelOrder."\r\n");
         fclose($file);
     }
     else
     {
         echo("Message delivery failed");
     }
 ?>

It works when I'm replacing the webform as http://localhost:8012/sendfromunity.php in line 51, but after uploading my game the local host url doesn't work. I've tried changing it to the url of my game but it still couldn't work.

I'm aware I might have made some silly mistakes or might have even misunderstood the entire tutorial; so if anyone could point me in the right direction I would be eternally grateful!