How to send attachments using php’s native mail function?

Question

How can I add an attachment that the person inserts into the form?

<?php
$action=$_REQUEST['action'];
if ($action=="")    /* display the contact form */
 {
?>
<center><h1>Formulário de forrnecedores</h1><br><br>
<form  action="" method="POST" enctype="multipart/form-data">
<input type="hidden" name="action" value="submit">
Seu nome:<br>
<input name="name" type="text" value="" size="30"/><br>
Seu e-mail:<br>
<input name="email" type="text" value="" size="30"/><br>
Nome do cliente:<br>
<input name="cliente" type="text" value="" size="30"/><br>
Marca/Tipo do tapete:<br>
<input name="tapete" type="text" value="" size="30" /><br>
Medidas:<br>
<input name="medidas" type="text" value="" size="30"/><br>
Detalhes Adicionais:<br>
<textarea name="message" rows="7" cols="30"></textarea><br>
<input type="submit" value="Send email" class="btn btn-primary"/>
</form>
<?php
}
else                /* send the submitted data */
{
$name=$_REQUEST['name'];
$email=$_REQUEST['email'];
$message=$_REQUEST['message'];
$tapete=$_REQUEST['tapete'];
$medidas=$_REQUEST['medidas'];
$cliente=$_REQUEST['cliente'];
if (($name=="")||($email==""))
   {
echo "Todos os campos devem ser preenchidos. Por favor, <a href=\"\">complete o formulário novamente</a>.";
   }
   else{
   $from="De: $name<$email>\r";
   $subject="Formulário FacilityCom";
   mail("[email protected]", $subject, "Tipo e marca: $tapete     \nMedidas: $medidas \nCliente: $cliente\n $from", $from);
   echo "<br> Email enviado!!";
   }