[php] Select mySQL based only on month and year

Here you go. Leave the computing to PHP and save your DB some work. This way you can make effective use of an index on the Date column.

<?php
    $date = $_POST['period'];

    $start = strtotime($date);
    $end   = strtotime($date . ' 1 month - 1 second');

    $query = sprintf(
        'SELECT *
           FROM projects
          WHERE Date BETWEEN FROM_UNIXTIME(%u) AND FROM_UNIXTIME(%u)',
        $start,
        $end
    );

EDIT
Forgot the Unix timestamp conversion.