my list of debugging functions to keep in an MU file

norcross-debug-functions.php

<?php
/*
Plugin Name: Norcross Debug Functions
Plugin URI: https://gist.github.com/norcross/7864205/
Description: A set of functions I use on all sites while building
Author: Andrew Norcross
Version: 0.0.1
Requires at least: 3.0
Author URI: http://andrewnorcross.com
*/

/**
 * Bypass the email sent for a successful auto-update.
 *
 * @param  bool   $send         Whether or not to send the email.
 * @param  string $type         The type of email to send. Can be one of 'success', 'fail', 'critical'.
 * @param  object $core_update  The update offer that was attempted.
 * @param  mixed  $result       The result for the core update. Can be WP_Error.
 *
 * @return bool                 The result to send the email.
 */
function rkv_bypass_auto_update_email( $send, $type, $core_update, $result ) {
	return ! empty( $type ) && 'success' === $type ? false : true;
}

add_filter( 'auto_core_update_send_email', 'rkv_bypass_auto_update_email', 10, 4 );


/**
 * Add a small bit of CSS to the Query Monitor output.
 *
 * @return void
 */
function rkv_add_qm_css() {
	echo '<style>#qm { position: relative; z-index: 1000; }</style>' . "\n";
}

add_action( 'wp_head', 'rkv_add_qm_css' );
add_action( 'admin_head', 'rkv_add_qm_css' );


/**
 * Keeps a user always logged in.
 * NOTE: Don't use this on a production site, ever!
 *
 * @return void
 */
function rkv_auto_login() {

	// Bail if the user is logged in.
	if ( is_user_logged_in() ) {
		return;
	}

	// Bail on ajax calls.
	if ( defined( 'DOING_AJAX' ) && DOING_AJAX ) {
		return;
	}

	// Don't load on a specific query string.
	if ( isset( $_GET['test-logout'] ) ) {
		return;
	}

	// Get our userdata (change the ID to match).
	$user   = get_userdata( 1 );

	// Bail if I don't have userdata.
	if ( empty( $user ) || ! is_object( $user ) ) {
		return;
	}

	// Set the current user.
	wp_set_current_user( $user->ID, $user->user_login );

	// Set the auth cookie.
	wp_set_auth_cookie( $user->ID );

	// Now actually log in.
	do_action( 'wp_login', $user->user_login );
}

add_action( 'init', 'rkv_auto_login' );
add_action( 'admin_init', 'rkv_auto_login' );


/**
 * Display array results in a readable fashion.
 *
 * @param  mixed   $display  The output we want to display.
 * @param  boolean $die      Whether or not to die as soon as output is generated.
 * @param  boolean $return   Whether to return the output or show it.
 *
 * @return mixed             Our printed (or returned) output.
 */
function preprint( $display, $die = false, $return = false ) {

	// Set an empty.
	$code   = '';

	// Add some CSS to make it a bit more readable.
	$style  = 'background-color: #fff; color: #000; font-size: 16px; line-height: 22px; padding: 5px; white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;';

	// Filter the style.
	$style  = apply_filters( 'rkv_preprint_style', $style );

	// Generate the actual output.
	$code  .= '<pre style="' . $style . '">';
	$code  .= print_r( $display, 1 );
	$code  .= '</pre>';

	// Return if requested.
	if ( $return ) {
		return $code;
	}

	// Print if requested (the default).
	if ( ! $return ) {
		print $code;
	}

	// Die if you want to die.
	if ( $die ) {
		die();
	}
}

/**
 * Grab the global WP_Query object and dump it.
 *
 * @param  boolean $die  Whether to die after generation.
 *
 * @return void
 */
function fullquery( $die = true ) {

	// Call the global WP_Query object.
	global $wp_query;

	// Output it.
	preprint( $wp_query, $die );
}


/**
 * Debugging Convenience function to show all the "filters" currently attached to a hook.
 *
 * @param  string  $hook  The hook to grab filters for.
 * @param  boolean $die   Whether to die after generation.
 *
 * @return mixed         Our printed output.
 */
function print_filters_for( $hook = '', $die = false ) {

	// Call the global wp_filter object.
	global $wp_filter;

	// Bail if no hook was provided or doesn't exist in the wp_filter object.
	if ( empty( $hook ) || ! isset( $wp_filter[ $hook ] ) ) {
		return;
	}

	// Output the information.
	preprint( $wp_filter[ $hook ], $die );
}

/**
 * Suppress errors generated by specified WordPress plugins.
 *
 * Include in the auto_prepend_file php.ini directive to ignore globally. Update
 * the directory separator as required.
 *
 * @see http://plugins.trac.wordpress.org/browser/ostrichcize/tags/0.1/ostrichcize.php#L146
 *
 * @param string $errno    The error number.
 * @param string $errstr   The error message.
 * @param string $errfile  Path to the file that caused the error.
 * @param int    $errline  Line number of the error.
 *
 * @return bool            True to success error reporting; false to use default error handler.
 */
function blazersix_wpdev_error_handler( $errno, $errstr, $errfile, $errline ) {

	// Set an array of plugin paths.
	$paths = array(
		'plugins\\wordpress-importer\\'
	);

	// Bail without paths.
	if ( empty( $paths ) ) {
		return false;
	}

	// Loop through our set plugin paths.
	foreach ( $paths as $path ) {

		// If we have the plugin path included in the error message, return true.
		if ( false !== strpos( $errstr, $path ) ) {
			return true;
		}

		// If we have the plugin path included in the file that caused it, return true.
		if ( false !== strpos( $errfile, $path ) ) {
			return true;
		}
	}

	// The path was not found, so report the error.
	return false;
}
set_error_handler( 'blazersix_wpdev_error_handler' );


/**
 * Parse a JSON file into more readable text.
 *
 * @param  string $text  The JSON text we want to parse.
 *
 * @return string $text  The JSON text we want to parse.
 */
function rkv_json_parse( $text = '' ) {
	return str_replace( array( '\n', '\t' ), '', $text );
}

/**
 * Set up some quick links for the admin bar.
 *
 * @param  WP_Admin_Bar $wp_admin_bar  The global WP_Admin_Bar object.
 *
 * @return void.
 */
function rkv_admin_bar_static( WP_Admin_Bar $wp_admin_bar ) {

	// Bail if current user doesnt have cap.
	if ( ! current_user_can( 'manage_options' ) ) {
		return;
	}

	// Remove customizer.
	$wp_admin_bar->remove_node( 'customize' );

	// Add a parent item.
	$wp_admin_bar->add_node(
		array(
			'id'    => 'norcross-dev-links',
			'title' => 'Dev Links',
		)
	);

	// Add the GitHub profile link.
	$wp_admin_bar->add_node(
		array(
			'id'        => 'github-profile',
			'title'     => 'GitHub Profile',
			'href'      => 'https://github.com/norcross/',
			'position'  => 0,
			'parent'    => 'norcross-dev-links',
			'meta'      => array(
				'title' => 'GitHub Profile',
				'target' => '_blank',
			),
		)
	);

	// Add the WP profile link.
	$wp_admin_bar->add_node(
		array(
			'id'        => 'wp-profile',
			'title'     => 'WordPress Profile',
			'href'      => 'https://profiles.wordpress.org/norcross',
			'position'  => 0,
			'parent'    => 'norcross-dev-links',
			'meta'      => array(
				'title' => 'WordPress Profile',
				'target' => '_blank',
			),
		)
	);
}
add_action( 'admin_bar_menu', 'rkv_admin_bar_static', 9999 );