PHP Code standared and Nameing convention

/*
my_function($para1, $para2)
$para1: string. string of something.
$para2: integer. number of something.
This function does some stuff, and other stuff.
Return: A string of something else.
*/
function my_function($para1, $para2){
     global $external_variables;
     # global variable should be declared at the top
     # a comment starts with a pound.
     #variable with two word, are separated by a underscore
     $my_var = "value of my var";
     ## coment section##
     # comments with more then one line, can use this format
     # or you can use /**/
     ###
}