1 developper is using the server, In the server's php.ini, xdebug.remote_host has to be set to your IP, either "localhost" if the server is on the same machine as PHPEdit, or an IP like "192.168.0.1", In the server's php.ini, xdebug.remote_port has to be set to the port PHPEdit is listening on, usually 9000
The server is shared by several developpers, In the server's php.ini, xdebug.remote_host has to be set to the IP if the DBGp proxy, either "localhost" if the server is on the same machine as the proxy, or an IP like "192.168.0.1", In the server's php.ini, xdebug.remote_port has to be set to the port the DBGp proxy is listening on, usually 9000
In PHPEdit's settings dialog, page "Misc" -> "Log", set Xdebug to "Debug"
Try to start a debug session
Make sure the "Log" dock is visible, check all the log levels in the toolbar, and see if there are errors in the list.
An incorrect version of php_xdebug.dll will fail silently
Make sure you put the breakpoint on a line containing code, that actually gets executed, The breakpoint is not on an empty line, The breakpoint is not on a comment line, The breakpoint is not on a line that never gets executed
Xdebug: Make sure Xdebug is loaded as a Zend Extension on your server, In the server's php.ini, Xdebug is loaded either with, Windows, zend_extension_ts="c:\full\path\to\your\extension\php_xdebug.dll" (< PHP 5.3), zend_extension="c:\full\path\to\your\extension\php_xdebug.dll", but not extension="c:\full\path\to\your\extension\php_xdebug.dll", Unix, zend_extension_ts="/full/path/to/your/extension/php_xdebug.so" (< PHP 5.3), zend_extension="/full/path/to/your/extension/php_xdebug.so", but not extension="/full/path/to/your/extension/php_xdebug.so", Xdebug doesn't appear twice in the server's php.ini
Xdebug: Check Xdebug's php.ini configuration, xdebug.extended_info is set to "On"
Make sure that your mapping settings are correct, In PHPEdit's debugger settings the local root, url root and remote root have to point to the same directory, from their respective point of views.
Xdebug: There's still communications between Xdebug and PHPEdit, you need to disable it, Either stop the Xdebug listener in PHPEdit, In the "Debugger" menu, "Stop Xdebug listener", Or disable Xdebug from your browser, Make sure Xdebug is not configured in autostart mode, In the php.ini, set xdebug.remote_autostart="off", Disable Xdebug by browsing to any url on your debug server and adding to the url XDEBUG_SESSION_STOP_NO_EXEC
Make sure that there's no output buffering going on on the server side, output_buffering is to be set to "Off" in the php.ini
Using PHPEdit 2.12 and Xdebug 2.0.3 or newer, A change in Xdebug 2.0.3 as made PHPEdit incompatible with it, Update to PHPEdit 3, or downgrade to an older version of Xdebug, until a new release of 2.12 with this issue fixed, http://www.xdebug.org/link.php?url=xdebug202
Something an outdate browser or browser plugin (like firebug for example) can slow down debugging, Try to use a different browser, and if it makes a change, to disable extensions in your usual browser to locate the extension causing the problem. Then try to update it to a newer version.