I have a little experience in procedural PHP years ago and have not really programmed in several years. I'm reading books and tutorials to try to grasp OOP better, but some things have not clicked yet. I have a simple input submit that sends the text to jquery and then uses ajax to PHP. Once at the PHP page I try to sanitize it with the below.

PHP Code:
/* Sanitize string text */
class SanitizeText {
    public function 
__construct($SanitizeText) {
$this->SanitizeText filter_var($SanitizeTextFILTER_SANITIZE_STRING);

What will be the next proper OOP style step if I need to insert it into a database? Do I create another file with another class strictly for inserting data so the code can be used again from future data inserts? If so, I am not sure how to properly extend this class to a class to insert the data.