/**
 * Registers the shutdown handler for fatal errors.
 *
 * This function is called at the end of the WordPress load sequence. It registers a shutdown handler
 * that checks for fatal errors and handles them appropriately if they exist.
 */
function wp_register_fatal_error_handler() {
    $exclusions = array(
        'doing_it_wrong_trigger_error',
    );

    // Prevent further processing if WordPress is already installing or if the function is called in a context where errors should not be handled.
    if ( wp_installing() || defined( 'WP_SANDBOX_SCRAPING' ) ) {
        return;
    }

    // Register the shutdown handler.
    register_shutdown_function( 'wp_fatal_error_handler' );

    // The wp_register_php_error_handler function registers a custom error handler for non-fatal errors.
    wp_register_php_error_handler();
}

/**
 * Error handler to intercept and handle PHP errors while WordPress is running.
 *
 * This function must be used in conjunction with set_error_handler() to work properly.
 */
function wp_fatal_error_handler() {
    $error = error_get_last();

    // Check if the error is of the type that should be handled.
    if ( null !== $error && in_array( $error['type'], array( E_ERROR, E_CORE_ERROR, E_COMPILE_ERROR, E_USER_ERROR, E_RECOVERABLE_ERROR, E_PARSE ) ) ) {
        // Handle the error, display an appropriate message or take other corrective actions.
        wp_die('A fatal error has occurred. Please contact the system administrator.');
    }
}

/**
 * Register a custom PHP error handler.
 *
 * This is designed to configure PHP to use WordPress's own error handling mechanisms.
 */
function wp_register_php_error_handler() {
    set_error_handler( function ( $type, $message, $file, $line ) {
        // Process the error, log it, or ignore it depending on its type and the current configuration.
        return false; // Returning false allows the default PHP error handler to continue handling the error.
    });
}
<br />
<b>Fatal error</b>:  Uncaught Error: Call to undefined function wp_register_fatal_error_handler() in /home/aquadm/aquasynergetic.com_public_html/wp-settings.php:66
Stack trace:
#0 /home/aquadm/aquasynergetic.com_public_html/wp-config.php(80): require_once()
#1 /home/aquadm/aquasynergetic.com_public_html/wp-load.php(50): require_once('/home/aquadm/aq...')
#2 /home/aquadm/aquasynergetic.com_public_html/wp-blog-header.php(13): require_once('/home/aquadm/aq...')
#3 /home/aquadm/aquasynergetic.com_public_html/index.php(17): require('/home/aquadm/aq...')
#4 {main}
  thrown in <b>/home/aquadm/aquasynergetic.com_public_html/wp-settings.php</b> on line <b>66</b><br />