Differences between filter_var and filter_input

Question

Why this doesn't work:

if(!($data['email'] = filter_var(INPUT_POST,'email',FILTER_SANITIZE_EMAIL)))
{
    $errors['email'] = 'Invalid Email.';
}

And this is working:

if(!($data['email'] = filter_input(INPUT_POST,'email',FILTER_SANITIZE_EMAIL)))
{
    $errors['email'] = 'Invalid Email.';
}

Difference here is filter_var and filter_input and when I hit submit whit filter_var doesn't submitting the form but with filter_input is submitted. Also here

filter_input(INPUT_POST,'email',FILTER_SANITIZE_EMAIL))

if I wrote for example some'@email.com why doesn't remove ' . Is it working this function? I'm a bit confused.

Answer 1

If you look at arguments filter_var and filter_input functions take, you will see why:

filter_var ($value_to_be_filtered, FILTER_TYPE, $options)

VS

filter_input($input_type , $variable_from_input, FILTER_TYPE, $options)

Where $input_type is one of INPUT_GET , INPUT_POST , INPUT_COOKIE , INPUT_SERVER , or INPUT_ENV .