simple php captcha contact form - php

Question

i am trying to create simple contact form with captcha in php. However it turns out implementing captcha is out of my league.
I found a simple answer on stackoverflow opn similar problem which pushed me 1 step closer to the end, but again i got stuck.
So i need a contact form that only check if text is entered and if correct captcha is answered, email is not mandatory.
</br>
<?php
$a=rand(2,9);
$b=rand(2,9);
$c=$a+$b;
if (isset($_POST['contact_text']) && isset($_POST['contact_email']) ) {
$contact_text = $_POST['contact_text'];
$contact_email = $_POST['contact_email'];
$recaptcha = $_POST['recaptcha'];
$info = 'Pranešimas apie korupciją: ';
$sender = 'Atsiuntė: ';
if (!empty($contact_text) && ($recaptcha == $c )) {
echo $recaptcha;
$to = 'muksinovas#gmail.com';
$subject = 'Korupcija';
$body = $sender."\n".$contact_email."\n".$info."\n".$contact_text;
$headers = 'From: '.$contact_email;
if (#mail($to,$subject, $body, $headers)) {
echo 'Jūsų pranešimas sėkmingai išsiustas. ';
} else {
} echo 'Įvyko klaida, bandykite dar karta.';
} else {
echo 'Neteisingai užpildyta forma.';
}
}
?>
<form action="contact1.php" method="post">
Pranešimas apie korupciją:<br><textarea name="contact_text" rows="6" cols="30" maxlength="1000" ></textarea><br><br> <!-- -->
Email (nebūtinas):<br><input type="text" name="contact_email" maxlength="30">
<?php echo $a."+".$b."="?><input type="number" name="recaptcha" maxlength="2" style="width:40px" />
<input type="submit" value="Siusti">
<br>
</form>
Now the problem is that I always get the message that details are incorrect. I tried to echo recaptcha just to see if $c is correct and it works. But for some reason not able to compare $recaptcha with $c or some other issue I am not sure.

Answer 1

The value of $c will be a completely different value when the user submits the contact form vs when your validation checks it. The value will change on every request because the script is re-interpreted.

Answer 2

You will have to save the value of $c on the initial page load, so that you can compare it afterwards in the next request. You can do that by storing it in $_SESSION.

Answer 3

You can write this
<?php
$min_number = 2;
$max_number = 9;
$random_number1 = mt_rand($min_number, $max_number);
$random_number2 = mt_rand($min_number, $max_number);
if (isset($_POST['contact_text']) && isset($_POST['contact_email']) ) {
$contact_text = $_POST['contact_text'];
$contact_email = $_POST['contact_email'];
$recaptcha = $_POST['recaptcha'];
$firstNumber = $_POST["firstNumber"];
$secondNumber = $_POST["secondNumber"];
$checkTotal = $firstNumber + $secondNumber;
$info = 'Pranešimas apie korupciją: ';
$sender = 'Atsiuntė: ';
if (!empty($contact_text) && ($recaptcha != $checkTotal )) {
echo $recaptcha;
$to = 'muksinovas#gmail.com';
$subject = 'Korupcija';
$body = $sender."\n".$contact_email."\n".$info."\n".$contact_text;
$headers = 'From: '.$contact_email;
if (#mail($to,$subject, $body, $headers)) {
echo 'Jūsų pranešimas sėkmingai išsiustas. ';
} else {
} echo 'Įvyko klaida, bandykite dar karta.';
} else {
echo 'Neteisingai užpildyta forma.';
}
}
?>
<form action="contact1.php" method="post">
Pranešimas apie korupciją:<br><textarea name="contact_text" rows="6" cols="30" maxlength="1000" ></textarea><br><br> <!-- -->
Email (nebūtinas):<br><input type="text" name="contact_email" maxlength="30">
<?php
echo $random_number1 . ' + ' . $random_number2 . ' = ';
?>
<input type="number" name="recaptcha" maxlength="2" style="width:40px" />
<input name="firstNumber" type="hidden" value="<?php echo $random_number1; ?>" />
<input name="secondNumber" type="hidden" value="<?php echo $random_number2; ?>" />
<input type="submit" value="Siusti">
<br>
</form>
This might solve your problem

Answer 4

you should to use session to solve your problem, i did little changes in your code, it should to work perfectly.
<?php
#session_start();
if (isset($_POST['contact_text']) && isset($_POST['contact_email']) ) {
$contact_text = $_POST['contact_text'];
$contact_email = $_POST['contact_email'];
$recaptcha = $_POST['recaptcha'];
$info = 'Pranešimas apie korupciją: ';
$sender = 'Atsiuntė: ';
if (!empty($contact_text) && ($recaptcha == $_SESSION["captcha"])) {
echo $recaptcha;
$to = 'muksinovas#gmail.com';
$subject = 'Korupcija';
$body = $sender."\n".$contact_email."\n".$info."\n".$contact_text;
$headers = 'From: '.$contact_email;
if (#mail($to,$subject, $body, $headers)) {
echo 'Jūsų pranešimas sėkmingai išsiustas. ';
} else {
} echo 'Įvyko klaida, bandykite dar karta.';
}else{
echo 'Neteisingai užpildyta forma.';
}
}else{
$a=rand(2,9);
$b=rand(2,9);
$c=$a+$b;
//setting captcha code in session
$_SESSION["captcha"] = $c;
?>
<form action="contact1.php" method="post">
Pranešimas apie korupciją:<br><textarea name="contact_text" rows="6" cols="30" maxlength="1000" ></textarea><br><br> <!-- -->
Email (nebūtinas):<br><input type="text" name="contact_email" maxlength="30">
<?php echo $a."+".$b."="?><input type="number" name="recaptcha" maxlength="2" style="width:40px" />
<input type="submit" value="Siusti">
<br>
</form>
<?php
}
?>