Help with AND OR == and !=

Hi
i have this code:

} elseif
($_POST["entidade1"] != "" && $_POST["morada1"] == "" || $_POST["codigo1"] == "" || $_POST["localidade1"] == "" || $_POST["telefone1"] == "" || $_POST["fax1"] == "" || $_POST["contribuinte1"] == "") {
echo "Por favor preencha os campos de facturação em branco<br>
<a href=\"Form1.html\">voltar</a>";

This is from a form, it’s supposed to check if the text field “entidade1” is filled. if it’s filled it’s required all other fields to be filled to.

by the way… i guess it’s better check if any field on this area is filled all other to be also filled.

Anyone to help me?

Thanks