Using the isset function vs. trim?

i think you missed something. isset() = this is a check function built into php example: if(isset($someVar)){ do something}; if something is set in any form run the code associated with it. trim() = is a function to remove spaces from the begin or end of a user submitted data field. example: " spaces in front and at the end " if the data in the quotes was submitted and you ran the trim function on the field it would remove the spaces from the begin and the end so it would read like "spaces in front and at the end".

they are used for different items trim removes spaces and htmlspecialchars converts special characters to html entities like & will be converted to & so they will be displayed properly. you can look them all up at http://php.net/manual/en/index.php