FILTER_VALIDATE_EMAIL saying a valid email is invalid

Question

I have a problem with checking if a email is valid. but the weird is that i have the same form on to different pages/urls, and on one of the forms it keeps saying that the email is invalid and on the form its valid.

The form on this page works - http://night.sendme.to/about the form on this page doesnt - http://night.sendme.to/book/jokeren

The HTML on the forms is the same

<form action="" method="post" id="myform">
        <div class="form-group">
            <label for="name">Navn *</label>
            <input type="text" class="form-control" id="name" name="name" placeholder="Navn" required="required">
        </div>
        <div class="form-group">
            <label for="corp">Virksomhed</label>
            <input type="text" class="form-control" id="corp" name="corp" placeholder="Virksomhed">
        </div>
        <div class="form-group">
            <label for="email">Email adresse *</label>
            <input type="email" class="form-control" id="email" name="email" placeholder="Email adresse" required="required">
        </div>
        <div class="form-group">
            <label for="tel">Telefon *</label>
            <input type="tel" class="form-control" id="tel" name="tel" placeholder="Telefon" required="required">
        </div>
        <div class="form-group">
            <label for="message">Kommentar</label>
            <textarea class="form-control" id="message" name="message" rows="10" required="required"></textarea>
        </div>
        <button type="submit" class="btn btn-default" id="submit">Send</button>
        </form>
        <div id="success" style="color:red;"></div>

The PHP is this

<?php   // Here we get all the information from the fields sent over by the form.
$name = $_POST['name'];
$email = $_POST['email'];
$message = $_POST['message'];

$to = 'YOURMAIL';
$subject = 'the subject';
$message = 'FROM: '.$name.' Email: '.$email.'Message: '.$message;
$header  = "MIME-Version: 1.0" . "\r\n";
$header .= "Content-type: text/html; charset=iso-8859-1" . "\r\n";
$header .= "from:".$_POST['email'];

if (filter_var($email, FILTER_VALIDATE_EMAIL)) { // this line checks that we have a valid email address
    mail($to, $subject, $message, $header); //This method sends the mail.
    echo "Your email was sent!"; 
    echo var_dump(filter_var($email, FILTER_VALIDATE_EMAIL)); 
} else {
    echo "Invalid Email, please provide an correct email.";
    echo var_dump(filter_var($email, FILTER_VALIDATE_EMAIL)); 
}
?>

The javascript is this

$(document).ready(function(){
    $('#submit').click(function(){
        $.post("email.php", $("#myform").serialize(),  function(response) {
        $('#success').html(response);
        //$('#success').hide('slow');
        });
        return false;
    }); 
});

Hope some one can help, why the form only works on the http://night.sendme.to/about and the others

Answer 1

So, to not leave this question answer-less:

In your HTML code, you actually had <form action="" method="post" id="myform"> in both pages – but in your second page, you had another <form> tag right before it … and because of this invalid HTML, the browser ignored the second form tag, and that made $("#myform").serialize() not return any data at all, because it could not find the form element with that id.

You should always validate your HTML code. This helps avoiding such errors.