Mira esto que te preparé:
Código PHP:
function cdm($dia = null, $mes = null, $anio = null) {
$timestamp = mktime(0,0,0,$mes,$dia, $anio);
return $timestamp;
}
function calendario($mes = null, $anio = null) {
$days = "";
$timestamp = cdm(1, $mes, $anio);
$cantidadDias = date('t', $timestamp);
$days .= '<ul>';
for ($day = 1; $day <= $cantidadDias; $day++) {
$days .= '<li>'. $day . " | " . date('l', cdm($day, $mes, $anio)) .'</li>';
}
$days .= '</ul>';
return $days;
}
echo '<div id="lista">';
echo calendario($mes = 10, $anio = 2012);
echo '</div>';