Debugging

YOURLS_DEBUG

In your user/config.php:

define('YOURLS_DEBUG', true);

Prints some debug info as well as the SQL query performed, in pages footer

Run SQL queries manually

Have PHPMyAdmin or something similar at hand. It's handy to run SQL queries manually when something doesn't feel right (for instance, a YOURLS update that doesn't work for you).

The all hook

In YOURLS 1.8.1+, you can define a custom function and hook all filters or actions (or both) that YOURLS triggers to it. Do NOT use this hook on a live site.

This is neat to better understand the flow of events within YOURLS, and debug plugins of course.

<?php
/*
Plugin Name: Minimalist Super Debug
Description: Small plugin, maxi verbose debug
Version: 0.1
Author: Ozh
*/

// If xdebug is on, make sure the var_dump() outputs are not trimmed
ini_set('xdebug.var_display_max_depth', '10');
ini_set('xdebug.var_display_max_children', '256');
ini_set('xdebug.var_display_max_data', '1024');


yourls_add_filter( 'all', 'ozh_superdebug', 10 );
yourls_add_action( 'all', 'ozh_superdebug', 20 );

function ozh_superdebug(...$args) {
    var_dump($args);
    var_dump( debug_backtrace() );
    echo "________________\n\n";
}

Note: If you want to trace filters and actions using the same function, you'll need as above to use a different priority so the second yourls_add_** doesn't overwrite the first one.

A slighly less verbose and more usable plugin:

<?php
/*
Plugin Name: List all actions and filters in the footer
Description: just as the name says
Version: 0.1
Author: Ozh
*/
ini_set('xdebug.var_display_max_depth', '10');
ini_set('xdebug.var_display_max_children', '256');
ini_set('xdebug.var_display_max_data', '1024');

// No direct call
if( !defined( 'YOURLS_ABSPATH' ) ) die();

global $ozh_debug;

yourls_add_action( 'all', 'ozh_debug_in_footer', 20 );
yourls_add_filter( 'all', 'ozh_debug_in_footer', 10 );
function ozh_debug_in_footer(...$args) {
    global $ozh_debug;
    $ozh_debug[] = sprintf("%s : %s", $args[0], $args[1]);
}

yourls_add_action('shutdown', 'ozh_debug_in_footer_print');
function ozh_debug_in_footer_print() {
    global $ozh_debug;
    echo "<pre style='text-align:left'>";
    print_r($ozh_debug);
    echo "</pre>";
}

Example output in the page footer:

Array
(
    [0] => filter : shunt_get_db
    [1] => filter : get_db
    [2] => action : plugins_loaded
    [3] => filter : kses_allowed_entities
    [4] => filter : kses_allowed_protocols
    [5] => filter : shunt_get_db
    [6] => filter : get_db
    [7] => filter : shunt_is_valid_user
    [8] => action : pre_login
    (...)