Tal vez te sirva
month de html5
Código PHP:
Ver original<form action="<?php echo $_SERVER['PHP_SELF'] ?>" method="post">
<input type="month" name="mes" value="
<?= date('Y-m') ?>">
<!-- -->
<input type="submit" value="Enviar" name="enviar">
</form>
<?php
echo $_POST['mes'];
?>