Sending Form Data Back to the Current Script

 <form action="<?php echo htmlspecialchars($_SERVER ['PHP_SELF']); ?>"> </form> 

All relevant browsers send back form data to the current page, if no action attribute is provided in the <form> element. However, the HTML and the Extensible Hypertext Markup Language (XHTML) specifications both state that action is a required attribute (marked as #REQUIRED in the Document Type Definitions [DTDs]). The behavior of the user agent is undefined, as the HTML specification at http://w3.org/TR/html4/interact/forms.html#adef-action explains. Therefore, it's a good idea to specifically provide the uniform resource locator (URL) of the current script as the form's action. the code above does this and also escapes special characters in $_SERVER['PHP_SELF'] for security reasons.