PHP常量在类内部设置，但是我现在需要在类外部进行更改，可以这样做吗？

Question

I have a simple core class that is being used for core functions to a small web app. I have defined some constants in the class - which has mostly static functions - and I am wanting to set / edit these constants outside of the class, example:

class core{
  const connection = '';
  public static function someSqlScript(){
    $sql = "SELECT * FROM sometable WHERE someconditions";
    $exec = mysqli_query(self::connection, $sql);  
  }
}

Now, I want to be able to set the connection constant so that it references a mysql connection object, which (by means of another script), has already been assigned to the variable $con, so essentially I am after something like this:

core::connection = $con; //send connection for use in class
core::someSqlScript(); //should not perform the MySQL query using conneciton $con as above

Any help is greatly appreciated, I am used to using non static functions and variables within classes, but the static functions with constants has got me.

Thanks to all.

Answer 1

The meaning of constant is, that you can't change it. You want a static variable :

class core{
  public static $connection = '';
  public static function someSqlScript(){
    $sql = "SELECT * FROM sometable WHERE someconditions";
    $exec = mysqli_query(self::$connection, $sql);  
  }
}

core::$connection = $con; 
core::someSqlScript(); 

Note the public static $connection instead of const connection and self::$connection instead of self::connection (also core::$connection instead of core::connection ).

Answer 2

常量的概念是，定义后不能更改它们。