PHP error: Undefined index: submit [duplicate] - php

Question

This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
PHP: “Notice: Undefined variable” and “Notice: Undefined index”
In this once the submit button is clicked it retrieve the data from database. But once i enter this page Undefined index: submit is shown before i click the submit button.
<div id="title">
<form method="get" action="<?php echo $_SERVER['PHP_SELF']?>">
<h3>Select your product and click submit</h3><br />
<select name="prod">
<option value="default">Select your product</option>
<option value="os">Operating Systems</option>
<option value="mobile">Smart Mobiles</option>
<option value="mobile">Computers</option>
<option value="shirt">Shirts</option>
</select><br /><br />
<input type="submit" value="Submit" name="submit"/>
</form>
The php code is:
<?php
$submitcheck=$_GET['submit'];
echo $submitcheck;
if (!isset($submitcheck)) {
echo 'Pls select and submit';
} else {
....
}
?>

Answer 1

You need to change your PHP to:
if (isset($_GET['submit']))
{
// Form has been submitted
}
else
{
// Form has not been submitted
}
At the moment, you're assigning a value which might not exist to $submitcheck and then checking whether it's set. You need to do it the other way round: check $_GET['submit'] is set, then assign it to a variable.

Answer 2

It's bacause you code is executed from top to bottom and on the top you are using $_GET['submit'] and then this key does not exist. You could do something like that:
if(array_key_exists('submit', $_GET)){
echo $_GET['submit'];
}
or even
if (!isset($_GET['submit']))
{
echo 'Pls select and submit';
}
else
{
....
}