PHP parentheses ( ), functions, keywords, etc.

Parentheses, keywords and functions follow the following rules:
a. Do not put parentheses and keywords closely together, but use a space to separate them; such as if ($a<$b);
b. There is no space between the parentheses and the function name; such as $test = date("ymdhis");
c. Do not use parentheses in Return statements unless necessary. Such as return $a;