Craig Francis

Features

PHP Form Setup

There are a number of ways to handle form submissions on websites.

One that seems to be quite popular, originally used in the good old days of the /cgi-bin/... this is where the <form> is put in a static HTML file, with its 'action' set to the URL of a server side script - which will either show a list of error messages, or a 'thank you' page.

However there are three fairly large problems:

If the data contains errors, the user will need to use their 'back' button - which in the wonderful world of Internet Explorer, means the user will return to an empty form.
If the data is valid, the user will be shown the 'thank you' page, where they can simply refresh the page to re-submit the data.
If the user links from your 'thank you' page, but later uses their browsers 'back' button, they will be presented with a message about the page expiring.

As an alternative, for the past few years I have been roughly using the following setup:

<?php

// ------------------------
// Get submitted values

$act = (isset($_POST['act']) ? $_POST['act'] : '');
$name = (isset($_POST['name']) ? $_POST['name'] : '');

// ------------------------
// No errors by default

$htmlErrors = array();

// ------------------------
// On form submission

if ($act != '') {

// ------------------------
// Validation

if ($name == '') {
$htmlErrors['name'] = 'Your name is required';
}

// ------------------------
// If there are no errors

if (count($htmlErrors) == 0) {

// ------------------------
// Process the data

mail(...);

// ------------------------
// Send to thank you page

goto('/contact/thankYou/');

}

}

?>
<form action="./" method="post">

<?php
if (count($htmlErrors) > 0) {
echo '<ul class="error">';
foreach ($htmlErrors as $htmlError) {
echo '<li>' . $htmlError . '</li>';
}
echo '</ul>';
}
?>

<input type="text" name="name" value="<?= html($name) ?>" />
<input type="hidden" name="act" value="submit" />
<input type="submit" value="Send" />

</form>

Some notes on this technique...

Its back to front, as the bit which processes the data is at the beginning.
If the data is invalid, the form will be re-displayed with a list of errors, and the fields will be re-populated though the 'value' attribute.
Only when the data has been accepted, does the user get sent to the static 'thank you' page.
Using the $htmlErrors array with the isset() function can be used to add an 'error' class on the input fields, to visually show which fields have the error.
I prefix variables with $html to show they contain HTML encoded data. In other words, all the variable data has gone though the htmlentities() cleaning process.
The goto() and html() functions are included in my basic website structure. See the PHP redirect article for more details of the goto() function, and why you should not use relative URLs in such a redirect.
The hidden 'act' field is used instead of a name on the submit button, as Internet Explorer wont send the value if the user pressed the [enter] key while the input field has focus.
It is possible to match exactly the value found in the 'act' field, but I prefer to check for a non-empty string, as it cuts down on the number of checks I need to make. However, it is useful if you need to distinguish between multiple forms on a page.

Thank you for looking at this code, any feedback would be greatly appreciated. If you would like to use this code, please read the licence it is released under.

Craig Francis

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