Xdebug will forever change the way you debug your PHP code

Tim Bond

Cascadia PHP Conference - September 21, 2019

What can Xdebug do?

Pretty formatting for var_dump
Stack traces for Notices, Warnings, Errors and Exceptions
Step debugger to use with IDEs
Profiler
Function call/variable assignment recording
Code coverage functionality for use with PHPUnit

var_dump

object(DateTime)#1 (3) { ["date"]=> string(26) "1970-01-01 00:00:00.000000" ["timezone_type"]=> int(3) ["timezone"]=> string(19) "America/Los_Angeles" }

object(DateTime)#1 (3) {
  ["date"]=>
  string(26) "1970-01-01 00:00:00.000000"
  ["timezone_type"]=>
  int(3)
  ["timezone"]=>
  string(19) "America/Los_Angeles"
}

var_dump

            xdebug.overload_var_dump=1

object(DateTime)[1]
  public 'date' => string '1970-01-01 00:00:00.000000' (length=26)
  public 'timezone_type' => int 3
  public 'timezone' => string 'America/Los_Angeles' (length=19)

Alternatively: xdebug_var_dump

Error messages

Notice: Trying to get property 'foo' of non-object in index.php on line 3

Error messages

xdebug.default_enable=1 #on by default

Other error reporting tricks

Scream: Show errors suppressed by @
Override PHP error display settings:
- force_error_reporting
- force_display_errors
Dump
Collection

Today's examples use PhpStorm

You can also use

Chrome
Dev-PHP
Eclipse
Emacs
KDevelop
Komodo
MacGDBP
NetBeans
Notepad++
PHPEdit
Protoeditor
pugdebug
Sublime Text
VIM
Visual Studio (and VS Code)
XDebugClient

Step Debugging

Pause script execution on a specific line
"Follow" code as it is executed
View/edit any variable
Execute arbitrary code

Installation

Windows, no PECL, or if all else fails:

pecl install xdebug

Mac, Linux

Installation Wizard

Download php_xdebug-2.6.1-7.2-vc15.dll
Move the downloaded file to C:\xampp\php\ext

Edit C:\xampp\php\php.ini and add the line

zend_extension = C:\xampp\php\ext\php_xdebug-2.6.1-7.2-vc15.dll

Restart the webserver

Docker?

version: '2'
services:
  webserver:
    image: phpstorm/php-73-apache-xdebug-27
    ports:
      - "80:80"
    volumes:
      - ./:/var/www/html
    environment:
      XDEBUG_CONFIG: remote_host=host.docker.internal

Try this docker-compose.yml and then docker-compose up

Pro Tip

Never edit php.ini
See "Scan this dir for additional .ini files" in phpinfo
Place an xdebug.ini file there

Confirm installation

Normal Request/Response

Request/Response with Debugger

Turn on settings

xdebug.remote_enable=1
xdebug.remote_autostart=1

xdebug.remote_connect_back=1
#Alternatively:
xdebug.remote_host=localhost

#Optional, default 9000
xdebug.remote_port=9000

Then restart the webserver

Turn on the debugger

Debugger states

Off

Breakpoints

Line on which to stop
Can only break where "something happens"
- Yes:
  - Function call
  - Variable assignment
- No:
  - Blank line
  - Curly brace

Setting a breakpoint

First Run (Zero Config)

The Debugger

Icons

Step Over

Step Into

Force Step Into

Step Out

Run to Cursor

Evaluate Expression

Add method to skip list

Icons

Resume

Stop

View Breakpoints

Mute Breakpoints

Frames

Variables

Demo

Then reload the page...

Step Back

lets you

code that you previously

Expression Evaluator

Conditional Breakpoints

Even More...

Wait, it's still not working!

Turn on profiler

xdebug.profiler_enable=1
xdebug.profiler_output_dir=C:\xampp\htdocs\

#XDEBUG_PROFILE GET or POST value
xdebug.profiler_enable_trigger=1

Then restart the webserver

Then reload the page...

Open the cachegrind.out.###### file

Execution Statistics

Call Tree

Questions

Bonus tip: Works for JavaScript too!

Bonus Tip: Xdebug with Docker on Mac

docker0 interface is actually on a VM

sudo ifconfig lo0 alias 10.254.254.254 255.255.255.0

https://gist.github.com/vranac/742127587bb57146e665c6a464cf497b

For a permanent solution:

So instead, alias the loopback adapter and send traffic there:

...this has to be run on reboots