xdebug的php作用有很多，我使用的原因是可以结合phpunit，通过单元测试查看代码覆盖率，作为自测参考。
安装步骤如下，其实就是源码目录中的READ文件内容（任何开源代码的README文件都很有必要读读），十分简单，希望对你有用，
1. Unpack the tarball: tar -xzf xdebug-2.2.x.tgz. Note that you do
not need to unpack the tarball inside the PHP source code tree.
Xdebug is compiled separately, all by itself, as stated above.
2. cd xdebug-2.2.x
3. Run phpize: phpize
(or /path/to/phpize if phpize is not in your path).
4. ./configure --enable-xdebug (or: ../configure --enable-xdebug
--with-php-config=/path/to/php-config if php-config is not in your
path)
5. Run: make
6. cp modules/xdebug.so /to/wherever/you/want/it
7. add the following line to php.ini:
zend_extension="/wherever/you/put/it/xdebug.so"
8. Restart your webserver.
9. Write a PHP page that calls "phpinfo();" Load it in a browser and
look for the info on the xdebug module. If you see it, you have been
successful!