Show error messages to a user when database insert fails

Question

I want to show a generic error message to a user when a database query fails on my site. I'm new to wordpress and I'm not sure how to go about it. I have the following function in my functions.php which gets called when the user submits a form:

function mytheme_insert_new_team() {

      $name  = $_POST['team_name'];
      $type  = $_POST['team_type'];
      global $wpdb;
      $table_name = "teams";
      $response = $wpdb->insert($table_name, array(
                                'team_name' => $name,
                                'team_type' => $type
                                ),array(
                                '%s',
                                '%s'));
            if(!$response){
                //an error has occured
            }else{
                //success, redirect user to the next step.
                mytheme_redirect_invite_others($name);
            }
}

I thought about echoing a "<p class='error'>An error occured.</p>" but it didn't work. I also tried using the $errors global but I couldn't seem to get that working either. I want to sent the error back to the page with the form and display it above the form. How do I do this?

Happy to provide more information if needed.

Thanks in advance for your help!

Answer 1

You should not use the $errors globally, but use hooks in WordPress development. Since you are new to WP development, I will explain briefly how it works.

What you should do instead:

1. make a new hook, or use an existing one which you call at the location you want this error to appear in your template file.
2. add the mytheme_insert_new_team function to this hook with add_action function

The syntax for this can be found here: https://code.tutsplus.com/tutorials/adding-custom-hooks-in-wordpress-custom-actions--cms-26454

A good explanation for how this exactly works is also found on that page under the section: Understanding WordPress Actions and then the subsection: Defining Custom Actions.

Here is the corresponding code I borrowed from that particular webpage:

<?php

/**
 * Define the action and give functionality to the action.
 */
 function tutsplus_action() {
   do_action( 'tutsplus_action' );
 }

 /**
  * Register the action with WordPress.
  */
add_action( 'tutsplus_action', 'tutsplus_action_example' );
function tutsplus_action_example() {
  echo 'This is a custom action hook.';
}

Now you have defined the action (hook) and registered the functionality to this hook with the 2nd part of the code.

Next, you want to make a call to this hook at the right location as following:

tutsplus_action()