How to convert date to datetime in PHP?

This post converting the Date format to DateTime format with beginning and end of that day in php.

1. Code:

    <?php 
	function convertDateToDateTime($str, $isFirstDay = true){
		if (!is_null($str) && trim($str) != ''
			&& strlen($str) <= 10) {
			$str .= $isFirstDay ? " 00:00:00" : " 23:59:59";
		}
		return $str;
	}
	$str = "20/06/2022";
	echo(convertDateToDateTime($str, false));
    ?>

2. Example:

Input:

$str = "20/06/2022";
convertDateToDateTime($str, false);
convertDateToDateTime($str, true)

Output:

20/06/2022 23:59:59
20/06/2022 00:00:00

PHP