YOu have to first understand the whole concept and role and purpose of each language which you are going to learn

The order must be - HTML and CSS (which help you to build the structure and style of your template design )
Jave Script, Jquery and mySql (which help you to function of you website (such as photo gallery, data input, show popups and results and enquiry form etc)and database management )

Then go to PHP..( which help you to manage outside data base like(enquiry form input data, dynamic features).