Trying to get variable from WP table and toggle its value

I have a query setup in a function to grab the payment status from a table in wordpress using a search string.
It will usually be ‘Completed’ (returned from paypal IPN).
All i’m trying to do is allow a local option to change the value string to another value and back again.
This is what i have so far:

 <!---TOGGLE PAYMENT STATUS--->

<?php function toggle_payment_status ()
        { 
           
 global $wpdb;
 $ipn_tables = $wpdb->prefix ."ipn_data_tbl";
 $searchIP = $_POST["searchIP"];
 
 $StatusCheck = $wpdb->get_var( $wpdb->prepare("SELECT payment_status FROM {$ipn_tables} WHERE serial_no = %s "),$searchIP);


  if ($StatusCheck = "Completed")   {
       $StatusCheck = "Refunded";
      } 
  
  else if ($StatusCheck = "Refunded")    {
      $StatusCheck = "Completed";
      }
                             
      $wpdb->update($ipn_tables, array(
          'payment_status' => $StatusCheck
                             ) , array(
            'serial_no' => $searchIP,
    ));
 }

When i run it the completed string changes to Refunded. A check in the Database shows the change. Great. So the $statuscheck should be this new ‘changed’ value of Refunded…but i don’t understand why the if statements are failing.
I did try elseif but not working either.
Could someone steer Mr dumbo in the right direction and explain what i did wrong?
Too much coffee & late nights hasn’t help. Thank you.

Answers:

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Method 1

There are two issues I see in your code:

1. The $searchIP is actually outside of the $wpdb->prepare(): (I didn’t use the full query so that you’d see the issue clearer)

   $StatusCheck = $wpdb->get_var( $wpdb->prepare("SELECT payment_status ..."),$searchIP);
   

   So you should correct that, like so: (reindented for clarity)

   $StatusCheck = $wpdb->get_var( $wpdb->prepare( "
       SELECT payment_status FROM {$ipn_tables}
       WHERE serial_no = %s
   ", $searchIP ) );
   

2. Your if should use the equality operator (== or ===) and not the basic assignment operator (=).

   So for examples, use if ($StatusCheck == "Completed") and if ($StatusCheck == "Refunded") instead of what you currently have in your code.

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