changing value of isset - php

Question

I'm wondering if it's possible to manually change the value of an isset value. That is, to do something like this:
isset($_POST['search_user']) = true;
Why I want to do this: I have two different "submit" forms on one page. When one form is submitted, I want to capture all the values of that form into SESSION variables. However, when the other form is submitted, the SESSION variables are wiped out (since the first form is not, technically, submitted anymore).
My idea was that, if the second form is submitted, then automatically set the value of the first form to true

Answer 1

If I understand your question correctly, if a second form is submitted, why not just destroy the current session and start new sessions using the variables posted from the new form?
http://php.net/manual/en/function.session-destroy.php
session_destroy();
...Or, you can set another session variable if the second form is submitted:
if (isset($_POST['search_user'])) {
$_SESSION['search_user'] = "true";
}
if ($_SESSION['search_user'] == "true") {
// Second form was submitted
}

Answer 2

You can try to define a name and a value for each submit button, so you retrieve this in the PHP file and do what you want, according you need. For instance:
HTML to the first form:
<form name="form1" action="page2.php" method="post">
<input type="submit" value="1" name="button01">
</form>
HTML to the second form:
<form name="form2" action="page2.php" method="post">
<input type="submit" value="1" name="button02">
</form>
Then you can detect the form thas was submited doing this in page2.php:
if($_POST['button01'] == "1")
{
// Do what you need based on form1 submit
}
elseif($_POST['button02'] == "1")
{
// Do what you need based on form2 submit
}
Try this and then leave some comment telling if it helps you.