PHP/MySQL query ignored if 'action' is set in form - php

Question

I basically have:
<form action="index.php" method="post">
<input name="text" type="text" value="Insert text here" size="20"/>
<input name="submit" type="submit" value="Submit" />
</form>
My PHP code then checks if submit is pressed:
if(isset($_POST['submit'])) {
$newDbValue = $_POST['text'];
$sql = ("
UPDATE `pseudo_tableName`
SET TEXT = '".$newDbValue."'
WHERE name = 'pseudo_fieldName' LIMIT 1
");
//SQL-query run by php function in separate class.
}
And as I understand it, if the form data is submitted it sends the user back to index.php?
But what mine does is it fails to update with new values and sends me back to index.php as if there was nothing wrong!
If I leave action="<?php $PHP_SELF; ?>" or action="" in the form, it updates when I reload the page (not F5 - click in address-line and hit enter).
What I want this to be:
I hit submit, and it updates the DB, sends me to index.php.
How can this be achieved?

Answer 1

Remove action="" (making you reload the page and using same file you have you if in) in your form and change your if to this:
if(isset($_POST['submit'])) {
$newDbValue = $_POST['text'];
$sql = ("
UPDATE `pseudo_tableName`
SET TEXT = '".$newDbValue."'
WHERE name = 'pseudo_fieldName' LIMIT 1
");
header("Location: index.php");
exit;
}

Answer 2

All <form> elements require the action attribute. What you're describing probably means your PHP script isn't detecting the form data and thus isn't making the necessary changes to your MySQL database. The reasons behind this may depend on the browser you're using; to my understanding, if you press Enter (keyboard) the submit button value isn't included in the form (this is said to allow multiple submit buttons with different value and perform the correct function).
If I were you, I'd check for the actual text input in the form, not the button.
<?php
// check 'text' exists and make sure it isn't blank.
if(isset($_POST['text']) && $_POST['text']!='') {
// do MySQL updating here.
header("Location: index.php"); // send back to index.php after updating.
}
?>
Because the most efficient method to redirect is to use header(); you're required to write your PHP form-checking script before the HTML form (because headers can't be send half-way through the actual document) so maybe at the top of the page before sending the HTML, additionally that way you can control what HTML is sent based on the processed data.

Answer 3

Have you tried setting:
<?php
if (isset($_POST['text']) AND !empty($_POST['text'])) {
// ...
}
?>
Instead of the other input?
The action='index.php' will send you back to index.php, so be sure that your PHP is above the form (and your HTML, for that matter). I also gues that you have set up your mysql_connect and you mysql_query functions.
Do you have error_reporting in php.ini on? What does the MySQL query result set say when you var_dump() the variable?
<?php
$sql = mysql_query($newDbValue));
var_dump($sql);
?>
That could really help you out.
The "cannot send header information - headers alredy sent" is because you have characters sent to the browser before the redirect() function - nothing can be sent to the browser (even whitespace!) if you're gonna use that, so be sure that the first thing in the document is your ?> tag, and your file encoding is UTF-8, not UTF-16 BOM or something crazy like that.