Php form validation, Post

Question

Here is my header for my form.

<form action="/page" id="landing_form" method="post" style="top:<?php echo get_post_meta($p->ID, 'top', true); ?>px; left:<?php echo get_post_meta($p->ID, 'left', true); ?>px;"  >

And a simple text field within my form, and submit button

<label>Email</label><input type="text" value="" id="landing_email" name="email" >
<input type="submit" name="submit" value="<?php echo get_post_meta($p->ID, 'button', true); ?>" class="landing_submit" id="landing_submit">

Now how would I make a function that checks if the email has a "."/"@" in it? Or is a specific string.

I have tried in my header to put something like onSubmit="return function('email);" and then putting the function within the file.

However it doesn't even check the function, and just submits the form regardless.

Answer 1

Assuming you want client-side validation you will have to create a javascript function like in this post

Therefore you will need your method:

<script>
function validateEmail(email) { 
    var re = /^(([^<>()[\]\\.,;:\s@\"]+(\.[^<>()[\]\\.,;:\s@\"]+)*)|(\".+\"))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$/;
    return re.test(email);
} 
function validate(email) {
    if (!validateEmail(email)) {
        return false;
    }

}
</script>

Then on the form you insert:

onSubmit="validate(email);"

This should not allow the form submission if the email is not valid. Please be aware that you will have to validate the email on the server side also.

Answer 2

the "onSubmit" attribute calls a piece of javascript when the submit button is pressed. It doesn't interact with your PHP at all.

What you'll probably want in your "page" page is something like the following:

<?php 
    if(isset($_POST['submit']))
    {
        $email = $_POST['email'];
        if(strpos($email, '@') && strpos($email, '.') && strpos($email, 'some specific string'))
        {
            // This code executes
            // only if there is an @
            // and a full stop and "some specific string"
            // inside the email
        }
    }
?>

Strpos is a function that searches for a substring within a string and returns the position of its first occurrence. If it cannot find the substring, it returns false.