Why is it important to pass strings as strings in PHP functions like date()?

When passing strings as arguments to PHP functions like date(), it is important to ensure that the argument is indeed a string. If a non-string variable is passed, it may result in unexpected behavior or errors in the function. To avoid this issue, always make sure to pass strings explicitly by enclosing them in quotes.

// Incorrect way of passing a non-string variable to date()
$date = date($format, $timestamp);

// Correct way of passing a string variable to date()
$date = date("$format", $timestamp);