Undefined variable that "is" defined?

Dev Shed Forums Sponsor:

December 25th, 2012, 05:30 PM

we5inelgr

Contributing User

Join Date: Jun 2012

Posts: 99

Time spent in forums: 21 h 59 m 39 sec
Reputation Power: 1

Undefined variable that "is" defined?

Hi all,

I've got a page (blah.html) that checks if a value is set for a select box. If it's not, then the select box is displayed with options. If it is set, then some other stuff is displayed.

First time into this page, $var1 is not set (as expected), so the select box is shown.

However, when either "This" or "That" is selected (i.e. $var1 then has a value) and the form is submitted, the expected result should be that the "Some other html" should be displayed. It's not. When I echo $var1, it always shows "" instead of "1" or "2" when either is selected. And, the php error says "Undefined variable" after a selection is made and the form is submitted.

Code:

<? if (!isset($var1)) { ?>
<form action="blah.html" method="post">

<select name="var1">
<option value="">-Select One-
<option value="1">This
<option value="2">That
</select>
</form>

<? } else { ?
Some other html.
<? } ?>

If "This" or "That" is selected on the first loading of the page, and then submitted, what would cause $var1 to *not* be set and thus not falling into the } else { where is should be after the submit?

December 25th, 2012, 07:21 PM

Jacques1

pollyanna

Join Date: Jul 2012

Location: Germany

Posts: 1,864

Time spent in forums: 1 Month 2 Weeks 1 Day 20 h 32 m 37 sec
Reputation Power: 813

Hi,

I don't see $var1 defined anywhere in the code. I hope you're not using the ancient register_globals?

What does your browser tell you about the POST request? Open the developer tools and check the form parameters.

December 25th, 2012, 08:16 PM

BarryG

Contributing User

Join Date: Aug 2011

Location: Sydney Australia

Posts: 131

Time spent in forums: 3 Days 7 h 51 m 28 sec
Reputation Power: 83

Quote:

Originally Posted by we5inelgr

Hi all,

First time into this page, $var1 is not set (as expected), so the select box is shown.

What do you think sets $var1 ?

You could get it like this

PHP Code:


		
			
 $var1 = $_POST['var1'];

Quote:

However, when either "This" or "That" is selected (i.e. $var1 then has a value)

Not until you assign it a value.

Unless you are using really old code that puts all your $_GET and $_POST variables into php variables, and that's not a good idea.

This code works, but NOT recommended

PHP Code:


		
			
<html>

<head>

</head>

<body><?php

 if (!isset($_POST['var1'])) {

 ?>

<form action="blah.php" method="post">



<select name="var1">

<option value="">-Select One-

<option value="1">This

<option value="2">That

</select>

<input type="submit" value="submit">

</form>



<?php } else { ?>

Some other html.

<?php } ?>

</body>

</html>

Also, if you want your ACTION file to do stuff, then it needs to be of a type that the server can parse, like php, not html.

You need to use proper php script tags too.

PHP Code:


		
			
<?  ?>

are shortcut tags and NOT supported everywhere.
You should use

PHP Code:


		
			
<?php  ?>

to mark up php code.

Bottom line. You are using a VERY old tutorial. You need to find something more up to date.

December 26th, 2012, 02:02 AM

we5inelgr

Contributing User

Join Date: Jun 2012

Posts: 99

Time spent in forums: 21 h 59 m 39 sec
Reputation Power: 1

Thanks for the replies guys.

$var1 is coming from the select box.

When the page first gets loaded, there is nothing selected and therefore no value.

When either option "This" or "That" is selected, and the form is submitted, I can see other variables on the resulting page...but for some reason the value from the select dropdown doesn't get set.

December 26th, 2012, 02:22 AM

we5inelgr

Contributing User

Join Date: Jun 2012

Posts: 99

Time spent in forums: 21 h 59 m 39 sec
Reputation Power: 1

If one of the items is selected from the dropdown, and the form submitted,

this fails to identify that $var1 has a value:
if (!isset($var1))

but this works:
if (!isset($_POST['var1']))