Understanding difference between __CLASS__, get_class(), and get_called_class() with underlying self/static keyword

late_static_bindings.php

<?php

/*#############################
* Developer: Mohammad Sharaf Ali
* Designation: Web Developer
* Version: 1.0
*/#############################

class c1
{
    public static $a = 1;
    
    public function f()
    {
        echo 'get_class:: ' . get_class();
        echo '<br />';
        echo '__CLASS__:: ' . __CLASS__;
        echo '<br />';
        echo '__CLASS__ using get_class:: ' . get_class(new self());
        echo '<br />';
        echo 'get_called_class()::' . get_called_class();
        echo '<br />';
        echo 'get_called_class() using get_class::' . get_class(new static());
        echo '<br />';
        
        echo 'self:: ' . self::$a;
        echo '<br />';
        echo 'static:: ' . static::$a;
        echo '<br />';
        echo '<br />';
    }
}

class c2 extends c1
{
    public static $a = 2;
}

echo ':: $c1->f() output ::';
echo '<br />';
$c1 = new c1();
$c1->f();

echo ':: $c2->f() output ::';
echo '<br />';
$c2 = new c2();
$c2->f();