Get First week day and last week day of current month in php.

// For First week day of current month
echo $first_week_day = date("Y-m-d", strtotime(date("Y").'W'.date('W')."0"));

// For Last week day of current month
echo $last_week_day = date("Y-m-d", strtotime(date("Y").'W'.date('W')."7"));