PHP Variables from HTML-forms

Variables in a PHP-script can get their value from a HTML-form (notice the use of the variable PHP_SELF):

<html> <body> <?php if ( $a ) { print( "a = $a" ); } else { // Form entry: print( "<form action=\"$PHP_SELF\" method=post>\n" ); print( "a = <input type=text size=10 name=a ><br>\n" ); print( "<input type=submit value=Submit>\n" ); print( "</form>\n" ); } ?> </body> </html>

Try it here.
One can of course still set the variable by test.php?a=23.

Keeping the state

A standard "trick" is to pass a variable in the generated links:

    ...
    <a href="edit_person_info.php?pid=27">Henrik Hulgaard</a>
    ...

In the edit_person_info.php script, there will typically be a form with the information for the person with id 27. When the form is submitted, the update-script needs to know the id. This is done by storing the id in a hidden field in the form:

    ...
    <input type=hidden name=pid value=<? echo $pid ?>>
    ...