WP_DEBUG Toggler. Toggle WP_DEBUG using a URL parameter.

wp-debug.php

<?php
/**
 * WP_DEBUG toggle for conveniently turning on and off from the a URL param "debug"
 * Its good when working on a staging site where you need debug functionality on/off
 *
 * usage: 
 * 
 *   Include this file in wp-config.php (include 'wp-debug.php';)
 *   Make sure to comment out all these constants in wp-config.php 
 *   
 *   WP_DEBUG, WP_DEBUG_LOG, WP_DEBUG_DISPLAY, SCRIPT_DEBUG
 *
 *   ?debug=1 will turn on debugging
 *   ?debug=0 will turn off debugging
 * 
 */


/**
 * Do not run the script if any of these constants is defined
 */
if ( 
  defined('WP_DEBUG') || 
  defined('SCRIPT_DEBUG') || 
  defined('WP_DEBUG_LOG') || 
  defined('WP_DEBUG_DISPLAY')
) {

  return;

}

$wp_debug = wp_debug();

// Enable WP_DEBUG mode
define( 'WP_DEBUG', $wp_debug );

// Enable Debug logging to the /wp-content/debug.log file
define( 'WP_DEBUG_LOG', $wp_debug );

// Disable display of errors and warnings
define( 'WP_DEBUG_DISPLAY', $wp_debug );
@ini_set( 'display_errors', ($wp_debug ? 1 : 0) );

// Use dev versions of core JS and CSS files (only needed if you are modifying these core files)
define( 'SCRIPT_DEBUG', $wp_debug );

/**
 * @return boolean 
 */
function wp_debug() {

  if ( session_status() === PHP_SESSION_NONE ) {

    @session_start();

  }

  $debug_toggle = isset($_GET['debug']) ? (int) $_GET['debug'] : null;

  if ($debug_toggle === 1) {

    $_SESSION['debug'] = 1;

  } else if ($debug_toggle === 0) {

    unset($_SESSION['debug']);

  }

  $debug = isset($_SESSION['debug']) && $_SESSION['debug'] == 1 ? true : false;
  $debug = $debug === false ? (isset($_GET['debug']) && (int) $_GET['debug'] === 1 ? true : false) : $debug;

  return $debug;

}