Debugging with WP_DEBUG in Wordpress - Step-by-Step Execution

Concept Flow - Debugging with WP_DEBUG

Enable WP_DEBUG in wp-config.php

↓

WordPress loads with debug mode ON

↓

PHP errors, warnings, notices are shown

↓

Developer reads error messages

↓

Fix code based on errors

↓

Disable WP_DEBUG after fixing

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Normal site runs

This flow shows how turning on WP_DEBUG helps catch errors by showing messages, guiding fixes, then turning it off for normal use.

Execution Sample

Wordpress

<?php
// In wp-config.php
define('WP_DEBUG', true);
// Trigger an undefined variable notice
echo $undefined_var;
?>

This code enables debugging and triggers a notice by using an undefined variable.

Execution Table

Step	Action	Evaluation	Result
1	Load wp-config.php	WP_DEBUG constant set to true	Debug mode enabled
2	Run echo $undefined_var;	Undefined variable used	PHP Notice displayed on screen
3	Developer sees notice	Reads message about undefined variable	Identifies bug location
4	Fix code by defining variable	Variable defined properly	No notice on reload
5	Set WP_DEBUG to false	Debug mode off	Site runs normally without debug messages

💡 Debugging complete, WP_DEBUG disabled for production

Variable Tracker

Variable	Start	After Step 2	After Step 4	Final
$undefined_var	undefined	undefined (notice shown)	defined with value	defined with value

Key Moments - 3 Insights

Why do I see error messages on my site after enabling WP_DEBUG?

When WP_DEBUG is true (see execution_table step 1), WordPress shows PHP errors and notices that normally stay hidden. This helps find bugs.

What happens if I leave WP_DEBUG enabled on a live site?

Leaving WP_DEBUG true on a live site shows errors to visitors, which can confuse users and expose sensitive info. Always disable after fixing bugs (see execution_table step 5).

Why does fixing the code stop the error messages?

Fixing the code (step 4) removes the cause of errors, so PHP no longer triggers notices or warnings, and debug messages disappear.

Visual Quiz - 3 Questions

Look at the execution table, what is the result at step 2?

A PHP Notice displayed on screen

B Debug mode disabled

C Variable defined properly

D Site runs normally

💡 Hint

Check the 'Result' column for step 2 in the execution_table

At which step does the developer fix the code to stop errors?

A Step 1

B Step 3

C Step 4

D Step 5

💡 Hint

Look at the 'Action' column describing fixing code in execution_table

If WP_DEBUG is set to false from the start, what changes in the execution?

A PHP errors are still shown

B No debug messages appear on screen

C Site crashes immediately

D Undefined variables become defined

💡 Hint

Refer to step 5 where WP_DEBUG is false and site runs normally

Concept Snapshot

WP_DEBUG is a WordPress constant to show PHP errors.
Set define('WP_DEBUG', true) in wp-config.php to enable.
Errors and notices appear on screen to help find bugs.
Fix code based on messages, then set WP_DEBUG false for live sites.
Never leave debug on in production to avoid exposing info.

Full Transcript

Debugging with WP_DEBUG means turning on a special setting in WordPress to see error messages. You do this by setting WP_DEBUG to true in the wp-config.php file. When enabled, WordPress shows PHP errors, warnings, and notices on the screen. This helps developers find and fix problems in their code. For example, using an undefined variable triggers a notice that appears on the page. After reading the message, the developer fixes the code to define the variable properly. Once fixed, the errors stop showing. Finally, WP_DEBUG is turned off to hide errors from visitors and keep the site clean. This process helps keep WordPress sites healthy and easier to maintain.