How to modify the MajorMode shortcut in emacs

We know that the format for modifying global shortcuts in emacs is as follows:

(Global-set-key key command)

For example, bind M-j to the find-file function as follows:

(Global-set-key (kbd "M-j") 'Find-file)

So, how do I modify the shortcut keys in a specific Major Mode?

The basic format is as follows:

(Global-set-key keymap key command)

Here there is a KEYMAP name, that is, each Major Mode has a KEYMAP name.

Take php-mode as an example. If I want to bind M-j to the find-file function in Major mode of php-Mode,

The method is as follows:

(Require 'php-mode) (define-key php-mode-map (kbd "M-j") 'Find-file)

Note: This requires php-mode first, and the corresponding KEYMAP name is found from the php-mode.el File