How to debug PHP functions with HHVM?

How to use HHVM to debug PHP functions: Install HHVM and Xdebug, and enable Xdebug in php.ini. Use the command line tool hhvm --gdb to start debugging mode. Set breakpoints and inspect variables in the IDE. An example demonstrates how to use HHVM to debug undefined variable errors, including command line and IDE integrated debugging steps.

How to debug PHP functions with HHVM

HHVM (HipHop Virtual Machine) is an open source runtime for executing PHP. It provides a powerful set of debugging tools that can help you quickly diagnose and fix problems in your code.

Installation and Setup

In order to use the debugging function of HHVM, you need to install HHVM and Xdebug. After the installation is complete, you need to enable the Xdebug extension in php.ini:

[xdebug]
zend_extension=/path/to/xdebug.so
xdebug.default_enable=On

Use command line debugging

Use HHVM's command line toolhhvm PHP scripts can be launched with debugging capabilities. To start debug mode, use the --gdb option:

hhvm --gdb index.php

This will start an HHVM session at the command line, where you can then set breakpoints and inspect variables.

Using IDE integrated debugging

Many IDEs (such as PHPStorm and NetBeans) support integrated debugging with HHVM. This allows you to set breakpoints and inspect variables directly from the comfort of the IDE.

Practical case: debugging undefined variable errors

The following is a sample script that demonstrates how to use HHVM to debug undefined variable errors:

<?php
$name = 'Alice';
echo $name . ' is ' . $age . ' years old.';

Run This script causes the following error:

PHP Fatal error:  Uncaught Error: Undefined variable: age in index.php:3

Debugging using the command line

To debug this error using HHVM's command line tools, use $gdb Options to start index.php:

hhvm --gdb index.php

Next, set a breakpoint where the variable $age is used, and run the script:

(gdb) breakpoint 3
(gdb) continue

The script will stop at the breakpoint and you can check the variable $age to confirm that it is undefined.

Use IDE integrated debugging

Using an IDE such as PHPStorm or NetBeans, you can set breakpoints and inspect variables directly in the IDE. This process varies depending on the IDE used. Please refer to your IDE's documentation for details.

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