What are common pitfalls when installing a PHP debugger extension?

Common pitfalls when installing a PHP debugger extension include not configuring the debugger properly in the php.ini file, not enabling the extension in the php.ini file, and not restarting the web server after making changes. To solve these issues, make sure to properly configure the debugger settings in the php.ini file, enable the extension by uncommenting the relevant line, and restart the web server to apply the changes.

```php
// Example of enabling Xdebug extension in php.ini file
zend_extension=xdebug.so
xdebug.remote_enable=1
xdebug.remote_host=localhost
xdebug.remote_port=9000
xdebug.remote_handler=dbgp
```
Remember to restart the web server after making these changes to ensure they take effect.