Singletone magic

gistfile1.php

<?php

trait singletone 
{
    static function getInstance() {
        static $instance;
        if ($instance === null){
            $instance = new self();
        }
        
        return $instance;
    }
}

class a {
    use singletone;
    
    private $name;
    
    
    public function test($i){
        self::getInstance()->name .= $i;
        echo "\ntestA" . self::getInstance()->name;
    }
}

class b {
    use singletone;
    
    private $name;
    
    
    public function test($i){
        self::getInstance()->name .= $i;
        echo "\ntestB" . self::getInstance()->name;
    }
}
a::getInstance()->test('1');
a::getInstance()->test('2');

b::getInstance()->test('3');
b::getInstance()->test('4');

a::getInstance()->test('5');

output:
-----
testA12
testB3
testB34
testA125