When an HTML form is submitted to a PHP page, the data becomes available to that script.
HTML Form
An HTML form has two required attributes : action and method. The action attribute specifies the script to which the form data is passed. For example, the following form submits one input property called myString to the mypage.php script file.
<!doctype html>
<html>
<body>
<form action="mypage.php" method="post">
<input type="text" name="myString">
<input type="submit">
</form>
</body>
</html>
The other required attribute of the form element specifies the sending method, which may be either GET or POST. ...