Do you know the case where you search for something within a PHPStorm project and want to jump back where you where before? Or that you jumped to a declaration of a function or to a usage of it?
Fortunately there is way to navigate back through your, lets call it, navigation stack. The shortcut for it is the following:
⌘ + ⌥ + ←
There are actually multiple shortcuts defined, you can check and change them through your keymap1. Search for "Back" (Main menu => navigate => back).
Preferences => Appearance & Behaviour => Keymap ↩