php time return day month year from datetime code example

Example 1: php get start and end date of month and year

<?php

$query_date = '2010-02-04';

// First day of the month.
echo date('Y-m-01', strtotime($query_date));

// Last day of the month.
echo date('Y-m-t', strtotime($query_date));

Example 2: get day of month php

// get day of month php
// Method 1; some server not work, I had check php 7.3.24 not worked, php 7.3.8 worked
cal_days_in_month(CAL_GREGORIAN, $month, $year)
echo (cal_days_in_month(CAL_GREGORIAN, 2, 2020)); // => 29

// Method 2;
function days_in_month($month, $year) {
    // calculate number of days in a month
    return $month == 2 ? ($year % 4 ? 28 : ($year % 100 ? 29 : ($year % 400 ? 28 : 29))) : (($month - 1) % 7 % 2 ? 30 : 31);
}

// Method 3;
echo (date('t', strtotime('2020-02-1')));	// 29