What are the debugging methods in PHP?

The debug (debugging) methods in PHP are: 1. Add echo, var_dump, print_r and exit statements in the PHP code, and print information through the browser for debugging; 2. Use Xdebug for debugging; 3. Through Console terminal for debugging.

The operating environment of this tutorial: Windows 7 system, PHP version 7.1, DELL G3 computer

Commonly used debugging methods for PHP

Debug by printing information from the browser

Method

Add echo, var_dump, print_r and exit, view the output in the browser.

Advantages and Disadvantages

Advantages:

• Simple, easy to use, no need to install plug-ins
• For the code you write , or a more familiar framework, you can use it like this

Disadvantages:

• For multi-branch logic, you need to add a lot of code or try multiple times
• For Unfamiliar logic cannot reflect the complete execution process.
• It is possible to leave debugging statements in the project
• Unable to single step

Tips

When debugging, In order to format output variables, you often need to implement your own dump() function in the project. Using Composer, the dump() function in the symfony/var-dumper package can be installed globally, making it available to all projects without modifying the project.

• Global installationsymfony/var-dumper Package:
  By default, it will be installed to the ${HOME}/.config/composer directory

composer global require symfony/var-dumper

• Modify the php.ini file and include the specified file before executing the PHP code

auto_prepend_file = ${HOME}/.config/composer/vendor/autoload.php

Use Xdebug Debugging

XDebug is a C/S structure, where Client is Xdebug installed in PHP, Server is the plug-in installed in IDE, and uses DBGP protocol to communicate. When PHP runs a script, it sends debugging information to the IDE through the Xdebug plug-in and receives control signals from the IDE.

You need to install and enable Xdebug for PHP, and then set up the IDE's Xdebug plug-in so that the two can communicate.

Advantages and Disadvantages

• Supports single-step debugging and acquisition of arbitrary variable values
• Complex configuration, requires IDE to install plug-ins
• Support cooperation with browsers, the request needs to carry XDEBUG_SESSION_START Parameters

Web App debugging

For web applications, To enable Xdebug debugging mode, additional flags must be added to the request sent by the browser. You can add XDEBUG_SESSION_START=session_name in the GET/POST/Cookie parameters, so that Xdebug will understand that this request needs to be debugged and connect to the IDE.

But it is troublesome to set it manually every time. There are two ways to simplify the operation:

• Use the method provided by the IDE. For PhpStorm, see Debugging PHP Web Applications with Run Debug Configurations. When using it, you need to configure the Web Server in the IDE, then set up a PHP Web Application, click the Debug button to start debugging, then the IDE will automatically open the browser and enter the URL, and add XDEBUG_SESSION_START=session_name.
• Use a browser plug-in and turn on the debugging switch of the plug-in. The plug-in can automatically bring the corresponding cookie in the request. For Chrome you can install Xdebug helper.

Debug through the console terminal (CLI mode)

For non-web applications, such as scheduled tasks or unit tests, you can directly Debugging in the console.

In PhpStorm, use the Alt F12 shortcut key to open the command line terminal. However, because only one terminal can be displayed in the IDE, the debugging terminal after debugging is turned on will cover the command line terminal, so it is better to open a separate command line terminal (you can use a DOS window or PowerShell under Windows).

Method and principle

Web applications debug requests through GET/POST/Cookie parameter flags, while non-web applications enable debugging by setting environment variables in the command line terminal. .

Two steps:

• Set environment variablesXDEBUG_CONFIG="idekey=session_name", this idekey needs to be matched with php.ini Some of the idekey settings are the same.
• Execute the script in the command line terminal. When executed, the debug terminal of the IDE will be evoked, allowing single-step debugging, and the output results will be displayed in the command line terminal in real time.

IDE usually provides shortcut operations. For PHPStorm, you can refer to Debugging PHP CLI scripts with PhpStorm.

After starting debugging through the IDE, the IDE will start the Xdebug plug-in to listen to a certain port (PhpStorm defaults to 9000, but this conflicts with PHP-FPM and can be changed to 9001) to obtain the debugging information returned by the PHP server.

D:\lnmp\php72\php.exe -dxdebug.remote_enable=1 -dxdebug.remote_mode=req -dxdebug.remote_port=9001 -dxdebug.remote_host=127.0.0.1 D:\lihongfeng\workspace\untitled\index.php

设置、查看和释放环境变量

• Linux

export XDEBUG_CONFIG="idekey=session_name" // 设置环境变量
echo $XDEBUG_CONFIG // 查看环境变量
unset XDEBUG_CONFIG // 删除环境变量

• Windows

set XDEBUG_CONFIG="idekey=session_name" // 设置环境变量
echo %XDEBUG_CONFIG% // 查看环境变量
set XDEBUG_CONFIG // 查看环境变量
set XDEBUG_CONFIG= // 删除环境变量

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