PHP and MYSQL Functions
PHP and mySQL have many built-in functions that can be used to alter all sorts of data. In some cases, there are functions in mySQL and PHP that do the same thing. For example, php and mySQL both have functions to make all text upper or lower case, remove whitespace, replace characters and encrypt strings in md5 or sha1...just to name a few.
It is good to know both. As you program, yiou will find a comfort zone and may lean on one method or another to achieve your goals. Since mySQL can be used with various programming languages like PERL or Python, strong mySQL skills and its function usage can already allow you to grasp what is happening in other code too.