A lightweight, high-performance PHP debugger extension. Forked from Xdebug by Derick Rethans, stripped down to pure debugging, and optimized for near-zero overhead when inactive.

• ~10% overhead when loaded but inactive (vs ~630% before optimization)
• Drop-in Xdebug replacement — existing configs, IDE setups, and workflows work unchanged
• Debug-only — no profiler, no coverage, no tracing. Just debugging, done right.
• Full DBGp protocol support — works with PhpStorm, VS Code, and any DBGp-compatible IDE

bench.php on Apple Silicon, PHP 8.5.3. No IDE connected — measures pure extension overhead.

Xdebug enables all hooks at startup regardless of trigger. PHP Debugger activates hooks only when a debug client is actually listening.

¹ Xdebug with mode=debug enables EXT_STMT unconditionally, so overhead is the same with or without a trigger.

curl -fsSL https://raw.githubusercontent.com/pronskiy/php-debugger-src/main/install.php | php

Installs the extension for the PHP it's run with — detects version and platform automatically.

pie install pronskiy/php-debugger

Grab the right binary from Releases, copy it to your extension directory, and add to php.ini:

zend_extension=php_debugger.so

PHP Debugger accepts both php_debugger.* and xdebug.* INI prefixes. Existing Xdebug configurations work as-is.

; Both of these work:
php_debugger.mode = debug
php_debugger.client_host = 127.0.0.1
php_debugger.client_port = 9003
php_debugger.start_with_request = trigger

; Xdebug-compatible (also works):
xdebug.mode = debug
xdebug.client_host = 127.0.0.1
xdebug.client_port = 9003
xdebug.start_with_request = trigger

Works as-is. PhpStorm connects via DBGp — the same protocol as Xdebug. Just swap the extension and your existing debug configurations work.

Works as-is with the PHP Debug adapter. No changes needed — it speaks DBGp.

PHP Debugger is a drop-in replacement for Xdebug's debug mode:

You can also use the new names — they work alongside the Xdebug ones:

• INI: php_debugger.mode, php_debugger.client_host, etc.
• Functions: php_debugger_break(), php_debugger_info(), php_debugger_connect_to_client(), php_debugger_is_debugger_active(), php_debugger_notify()
• Triggers: PHP_DEBUGGER_SESSION, PHP_DEBUGGER_SESSION_START, PHP_DEBUGGER_TRIGGER

• PHP 8.2, 8.3, 8.4, or 8.5

Released under The Xdebug License, version 1.03 (based on The PHP License).

This product includes Xdebug software, freely available from https://xdebug.org/.

PHP Debugger is built on the foundation of Xdebug, created and maintained by Derick Rethans since 2002. His two decades of work on PHP debugging tools made this project possible. Thank you, Derick.