Incoming Connection Dialog
The dialog is available only when the PHP plugin is enabled. The plugin is not bundled with IntelliJ IDEA, but it can be installed from the JetBrains plugin repository as described in Managing plugins.
The dialog opens when you initiate a Zero-Configuration debugging session without previously configuring a Debug Server with path mappings, so the debugger cannot set correspondence between the scripts in the running application and the files in your IntelliJ IDEA project.
The upper part of the dialog is read-only and shows the host and port where the script is executed, the path to the script relative to the server document root, and the absolute path to the script on the server.
In this dialog, either specify the path mappings manually or import them from the relevant deployment configuration. Learn more at Creating a PHP Debug Server Configuration, Configuring synchronization with a web server, and Zero-Configuration Debugging.
Import mappings from deployment
Choose this option to use the mappings specified in a server access configuration (deployment configuration.).
Manually choose local file or project
When you select this option, IntelliJ IDEA displays the project tree view where you can select a project file and map the currently executed script to it. You can also select and map the entire project.