trying to understand late static bindings in php

Question

<?php
class Record {

    protected static $tableName = 'base';

    public static function getTableName() {
        echo self::$tableName;
    }
}
class User extends Record {
    protected static $tableName = 'users';
}
User::getTableName(); 

It shows: base

Question:

I know I can change the problem by changing this line echo self::$tableName; to echo static::$tableName;, it is called 'late static bindings', I read the doc here, but still not quite understand it. So could you give me some explanation on:

a. why this line of code echo self::$tableName; shows: base?

b. why this line of code echo static::$tableName; shows: users?

Answer 1

The example below will give a minimum example of late static binding:

class A {
    static public $name = "A";

    static public function getName () {
        return self::$name;
    }

    static public function getNameLateStaticBinding () {
        return static::$name;
    }
}


class B extends A {
    static public $name = "B";
}



// Output: A
echo A::getName(), "\n";

// Output: A
echo B::getName(), "\n";

// Output: B
echo B::getNameLateStaticBinding() , "\n";

B::getName() outputs the $name variable from A since self is computed from the absolute current class you defined self in. To solve such cases, use static.