MySQL: Seperation with "," when concatenating two strings

Hi guys,

Have a little problem when using MySQL through unity. I am trying to receive a string from a (VARCHAR) table in MySQL, and when received, i want to combine it with another string. Each string should be separated by a "," so for example if I receive a "3" and want to add a "5", the result should be "3,5".

I connect through Unity to a .php script on my server which gets the existing string of the table, as seen in the GetUserProjectId(). Afterwards I call the AddToUserProjectId() which takes the existing string "userProjectIdString" and the new string "projectId.ToString()" and forwards them to another .php script.

 function GetUserProjectId(){
     var URL = "http://getsharp.net/getUserProjectId.php"; //change for your URL
     userId = userId+1;
     var form = new WWWForm(); //here you create a new form connection
     form.AddField( "myform_hash", hash ); //add your hash code to the field myform_hash, check that this variable name is the same as in PHP file
     form.AddField( "myform_userId", userId );
     var w = WWW(URL, form); //here we create a var called 'w' and we sync with our URL and the form
     yield w; //we wait for the form to check the PHP file, so our game dont just hang
     if (w.error != null) {
         print(w.error); //if there is an error, tell us
     } else {
         formText = w.text; //here we return the data our PHP told us
         w.Dispose(); //clear our form in game
     }
     
     userProjectIdString = formText;
     
     AddToUserProjectId();
     
 }


 function AddToUserProjectId(){
     var URL = "http://getsharp.net/addToUserProjectId.php"; //change for your URL
     var form = new WWWForm(); //here you create a new form connection
     form.AddField( "myform_projectIdExisting", userProjectIdString );
     form.AddField( "myform_projectIdNew", projectId.ToString() );
     form.AddField( "myform_userId", userId );
     form.AddField( "myform_hash", hash ); //add your hash code to the field myform_hash, check that this variable name is the same as in PHP file
     var w = WWW(URL, form); //here we create a var called 'w' and we sync with our URL and the form
     yield w; //we wait for the form to check the PHP file, so our game dont just hang
     if (w.error != null) {
         print(w.error); //if there is an error, tell us
     } else {
         formText = w.text; //here we return the data our PHP told us
         w.Dispose(); //clear our form in game
     }
     print(formText);
 }

There is no problem adding a "," between the two strings in my .php script called "addToUserProjectId.php", and updating the string to my table, but it is when I want to receive the existing string from "getUserProjectId.php" that the error occurs. The .php script automatically removes the "," and just gives me a string only with numbers. Below is the .php code that selects the existing string from the database.

 $userId = anti_injection_login($_POST["myform_userId"]);
 if ($unityHash != $phpHash){
         echo "HASH code is different from your game, you infidel.";
     } else {
         $sql = mysql_query("SELECT projectId FROM users WHERE id='$userId'");
         while($result = mysql_fetch_array($sql)) {
         $projectId = $result["projectId"];
         $data = $projectId;
         echo $data;
         }
 }

And just so I am sure that there is no error when updating the table, below is the code from the .php script where I update my table with the two strings:

 $projectIdExisting = anti_injection_login($_POST["myform_projectIdExisting"]); //I use that function to protect against SQL injection
 $projectIdNew = anti_injection_login($_POST["myform_projectIdNew"]);
 
 if($projectIdExisting == null){
     $idToInsert = $projectIdNew;
 }else{
     $idToInsert = $projectIdExisting.",".$projectIdNew;
 }
 
 $userId = anti_injection_login($_POST["myform_userId"]);
 
 if ($unityHash != $phpHash){
         echo "HASH code is different from your game, you infidel.";
     } else {
         
         $query = "UPDATE users SET projectId='$idToInsert' WHERE id='$userId'";
 
         mysql_query($query) or die ('Error updating database');
     
         echo"Database updated";
 }

Anybody see a problem?

Thanks.