DateTimeImmutable.md

DateTimeImmutable vs DateTime

• DateTime示例

    $date = new DateTime();
    $tomorrow = $date->modify('+1 day');
    echo $date->format('Y-m-d');
    echo $tomorrow->format('Y-m-d');	
  

  • This will output:

      2021-05-15
      2021-05-15
    

  • What happened here is that the modify returned the same instance of the DateTime object. The variable $tomorrow doesn't contain a different object, it contains a reference to the original one.

• DateTimeImmutable示例

    $date = new DateTimeImmutable();
    $tomorrow = $date->modify('+1 day');
    echo $date->format('Y-m-d');
    echo $tomorrow->format('Y-m-d');	
  

  • This will output:

      2021-05-14
      2021-05-15
    

  • Because in DateTimeImmutable, the modification methods don't return the same instance, they give you a fresh one (also immutable).