What are some best practices for converting and manipulating timestamps in PHP to accurately represent dates and times in database queries?

When converting and manipulating timestamps in PHP to accurately represent dates and times in database queries, it is important to use the appropriate PHP date and time functions to ensure consistency and accuracy. One common practice is to store timestamps in the database as Unix timestamps (integer values representing the number of seconds since January 1, 1970). When querying the database, these Unix timestamps can be easily converted to human-readable date and time formats using PHP date functions.

// Convert a Unix timestamp to a human-readable date format
$timestamp = 1609459200; // Example Unix timestamp
$date = date('Y-m-d H:i:s', $timestamp);
echo $date; // Output: 2021-01-01 00:00:00

// Convert a human-readable date format to a Unix timestamp
$date = '2021-01-01 00:00:00'; // Example date
$timestamp = strtotime($date);
echo $timestamp; // Output: 1609459200