PHP MySQLi connection and query error handling. How?

Solution:

Here’s is the final tested and working PHP solution for all to see.

<?php  

  /* Status Codes

     return 0 = Nothing to Update
     return 1 = Successful Update Query
     return 2 = Database Connection refused
     return 3 = MySQL Query Error OR Wrong URL Parameters */

  mysqli_report(MYSQLI_REPORT_STRICT);

  if(isset($_GET["postT_VAL"])) {

  $client_id    = $_GET["postCLIENT_ID"];
  $project_id   = $_GET["postPROJECT_ID"];
  $mainsheet_id = $_GET["postMAINSHEET_ID"];
  $field_name = $_GET["postT_ID"];
  $field_value = $_GET["postT_VAL"];

  try {
       $link = mysqli_connect("domain", "username", "password", "database");
  } catch (Exception $e) {
       // echo "".$e->getCode();
       /* return 2 = Database Connection refused */
       echo "2";

       exit;
  }

  /* Build dynamic Update Query string */
  $sql = "UPDATE tbl_mainsheet2 SET ".$field_name." = '".$field_value."' WHERE client_id = '".$client_id."' AND project_id = '".$project_id."' AND mainsheet_id = '".$mainsheet_id."'";  

  /* Execute Update Query */    
  if(!mysqli_query($link, $sql)) {

  echo "3";
  /* Close Connection */
  mysqli_close($link);

  exit;

  } else {

  /* return 0 = Nothing to Update / 1 = Successful Update Query */
  echo "".mysqli_affected_rows($link);

  /* Close Connection */
  mysqli_close($link);

  }

 }

?>