Register New File Type Association Dialog
The dialog box opens when you attempt to open a file in the editor, but PhpStorm does not recognize its type by the file extension. Use the dialog box to associate unknown file extensions with existing file types.
Open matching files
When this option is selected, PhpStorm treats the type of the file to be opened as one of the recognized file types. Choose the relevant type from the list box below, that displays all the file types recognized by PhpStorm.
In this text box, specify the file pattern to be associated with the selected file type. By default, the text box shows the following pattern:
Open matching files in associated application
When this option is selected, PhpStorm attempts to open the selected file using its native application, if this application is available.