How can i know when i can execute what functions of wordpress?

Install my plugin T5 WP Load Order. You get a long detailed list with all available hooks, files, constants, classes, functions and global variables – ordered by first appearance.

Whenever you’re in doubt create such a list for the page you are working on, and look up what you need.

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)