How to found out extra fields in Symfony2 form?

If you encounter this error message while working with Symfony2 forms, follow my advice.

This form should not contain extra fields.

This way to find out the fields that are considered "extra" is very simple. I use the code quite frequently. Here it is:

$data = $request->request->all();

print("REQUEST DATA<br/>");
foreach ($data as $k => $d) {
    print("$k: <pre>"); print_r($d); print("</pre>");
}

$children = $form->all();

print("<br/>FORM CHILDREN<br/>");
foreach ($children as $ch) {
    print($ch->getName() . "<br/>");
}

$data = array_diff_key($data, $children);
//$data contains now extra fields

print("<br/>DIFF DATA<br/>");
foreach ($data as $k => $d) {
    print("$k: <pre>"); print_r($d); print("</pre>");
}
...
$form->bind($data);

Have a nice day!