Xdebug successfully connects to DBGP clients, but won't stop at breakpoints

Question

I have Xdebug 2.1 installed, and running with PHP 5.2.13. It can successfully connect to multiple DBGP clients (i.e. the xdebug.remote_log shows communication

Answer 1

This appears to happen if you have have Xdebug loaded as an extension (i.e. extension=xdebug.so) in the PHP config instead of a zend_extension (i.e. zend_extension=/usr/lib/php5/20060613+lfs/xdebug.so).

Make sure that you don't have an extension=xdebug.so line anywhere in your PHP config, even if you're pretty sure you're using zend_extension. For example, if you have zend_extension in /etc/php5/conf.d/xdebug.ini, this may well be superseded by an extension in /etc/php5/apache2/php.ini. If this is the case, nothing will complain, and phpinfo() will dutifully report that Xdebug is loaded! (Xdebug 2.1 does issue a small warning in phpinfo() when loaded as an extension, but previous versions do nothing.)