Kako preveriti ali so vnosna polja izpolnjena?

To, da bi lahko naredil v sami mail.php datoteki, sem se spomnil najprej, ker bi enostavno preverjal dolžine spremenjljivk, vendar si v tem koraku že na novi strani(mail.php) in se mora uporabnik vračati na obrazec.

if ($_POST['ime_form_post_gumba'])
{
  // tu notri pa pride najprej validacija, kot je že nekdo napisal

  if ($_POST['prva_spremenljivka'] && $_POST['druga_spremenljivka'] && ...)
  {
    // vstavi kodo, ki obdela podatke (recimo vstavi v bazo, pošlje mail,...
    // ko obdelaš podatke pa preusmeri uporabnika na stran, kamor želiš s header()
    header("Location: index.php"); // recimo
  }
  else
  {
    // vstavi kodo, ki izpiše problem. Recimo:
    $error = 'Niste izpolnili vseh polj';
  }
}

<input type="text" name="ime" value="<? echo $_POST['ime']; ?>" /> 

if ($error)
{
  echo $error;
}

<?php

// Change these two variables to meet your needs.

$myemail = 'mail@mail.com';
$subject = 'Feedback from the website';

$op = $_POST[op];

if($op == 'contact')
{
    $name = stripslashes($_POST[name]);
    $email = stripslashes($_POST[email]);
    $text = stripslashes($_POST[text]);
    $referer = $_POST[referer];
    $remote_host = $_SERVER[REMOTE_ADDR];
    $server = $_SERVER[SERVER_NAME];
    $browser = $_SERVER[HTTP_USER_AGENT];

    if(!eregi("^[_a-z0-9-]+(.[_a-z0-9-]+)*@[a-z0-9-]+(.[a-z0-9-]+)*(.[a-z]{2,3})$",$email)) 
    { 
        $status = "We're sorry, but you've entered an incorrect email address.<br>";
    }
    if(!$name)
    {
        $status .= "Please enter your name.<br>";
    }
    if(!$text)
    {
        $status .= "Please enter a message.<br>";
    }

    if(!$status)
    {
        $header = "From: $emailrnReply-To: $emailrn";

        $message = "
            Name: $name
			Mail: $email
            Referer: $referer
            Site: $server
            Remote Host: $remote_host
            Remote Browser: $browser

            $text
        ";

        if(mail($myemail, $subject, $message, $header))
        {
            $status = "Thank you for your Feedback!<br>";
        }
        else
        {
            $status = "There was a problem sending your feedback, please try again later.<br>";
        }

    }
    else
    {
        $status .= "<br>Please press back on your browser to resubmit.<br>";
    }
}    

// Now check the referer page and ensure it's a proper URL

$referer = $_SERVER[HTTP_REFERER];

if(!preg_match('#^http\:\/\/[a-z0-9-]+.([a-z0-9-]+.)?[a-z]+#i', $referer))
{
    unset($referer);
}

?>

<?php print $status; ?>

<form style="text-align: center;" method="post" action="<?php print $_SELF; ?>">
<input type="hidden" name="op" value="contact">
<input type="hidden" name="referer" value="<?php print $referer; ?>">
Name:<br>
<input class="form_fields1" name="name" size="35" style="width: 190px;" value="">
<br>
e-mail:
<br>
<input class="form_fields1" name="email" size="35" style="width: 190px;" value="">
<br>
Message:<br>
<textarea class="form_fields2" name="text" cols="26" style="width: 220px;" rows="8"></textarea>
<p />
<input type="submit" value="Submit">
</form>