condition before submitting php form - php

Question

I have a page with an options menu, however would like the user to pass the captcha test. Currently i want it so the user enters atleast 3 characters in the textbox or else they would not be able to submit the form, the code is shown below with the php condition at the end of the form. However i know i have obviously got it wrong. Is there anyway to do this without pasting the php code on another page? Thanks.
<?php
// Check to see if the form has been submitted.
if(isset($_POST['menu1'])) {
// If the form has been submitted, force a re-direct to the choice selected.
header('Location: ' . $_POST['menu1']);
}
?>
<div style="padding-left: 50px">
<p class="arial"><strong></strong><br /><br /></p>
<form method="post">
<table class="freecontact2form" border="0" width="400px">
<tbody>
<tr>
<td colspan="2"><span style="font-size: x-small;"> </span> <font color=#000000 >Which of the following do you want to use?</font>
<br /><br /></td>
</tr>
<tr>
<td valign="top"><table width="400px" class="freecontact2form">
<tr>
<td colspan="2"><br />
<br />
<div class="freecontact2formmessage"> </div></td>
</tr>
<tr>
<td valign="top"><label for="menu1" >The options are:<span class="required_star"> </span></label></td>
<td valign="top"><select name="menu1" id="menu1">
<option selected="selected" value ="http://www.google.com">Google </option>
<option value ="http://www.yahoo.com">Yahoo</option>
<option value ="http://www.bing.com">Bing</option>
</select></td>
</tr>
<tr>
<td valign="top"><label for="captcha" ><span class="required_star"></span><span class="required_star"></span></label></td>
<td valign="top"><BR /><BR /><img src="captcha.jpg" /></td>
</tr>
<tr>
<td>Please enter the characters shown in the CAPTCHA image:</td>
<td><input type="text" name="captcha" id="captcha" value="" size="10" />
</td>
</tr>
<tr>
<td style="text-align:center" colspan="2"><br /><br />
<input type="submit" value=" Submit ">
</td>
</tr>
</table></td>
<td valign="top"> </td>
</tr>
</tbody>
</table>
</form> <br />
<p> </p>
<p> </p>
<?php
if(isset($_POST['menu1'])) {
function died($error) {
echo "Sorry, but there were error(s) found with the form you submitted. ";
echo "These errors appear below.<br /><br />";
echo $error."<br /><br />";
echo "Please go back and fix these errors.<br /><br />";
die();
}
if(!isset($_POST['menu1']) ||
!isset($_POST['captcha'])
) {
died('Sorry, there appears to be a problem with your form submission.');
}
$error_message = "";
if(strlen($captcha) < 3) {
$error_message .= 'Please ensure the captcha entered is at least 3 characters long';
}
if(strlen($error_message) > 0) {
died($error_message);
}
?>
<?php
}
die();
?>

Answer 1

Try this code at the top of your file (instead of at the bottom). Notice I fixed a few issues.
First, you were doing the header() redirect before ever running your validation code, because that was at the top of your file while the validation was below. I changed the logic so if the validation succeeds, then it will redirect, otherwise it will show an error message
Second, you were checking strlen($captcha) but should have been checking strlen($_POST['captcha']).
<?php
function died($error) {
echo "Sorry, but there were error(s) found with the form you submitted. ";
echo "These errors appear below.<br /><br />";
echo $error."<br /><br />";
echo "Please go back and fix these errors.<br /><br />";
die();
}
if(isset($_POST['menu1'])) {
if(!isset($_POST['menu1']) || !isset($_POST['captcha'])) {
died('Sorry, there appears to be a problem with your form submission.');
}
$error_message = "";
if(strlen($_POST['captcha']) < 3) {
$error_message .= 'Please ensure the captcha entered is at least 3 characters long';
}
if(strlen($error_message) > 0) {
// VALIDATION ERRORS, DIE
died($error_message);
}
else {
// DO YOUR REDIRECT RIGHT HERE... NO VALIDATION ISSUES, CONTINUE...
header('Location: ' . $_POST['menu1']);
}
}
?>

Answer 2

You have to keep the captcha in session first and then check it with the value submitted in order to match them after validating that entered value is of 3 character or more.