PHP: self vs $this

Self:
-self refers to the current class
-self can be used to call static functions and reference static member variables
-self can be used inside static functions
-self can also turn off polymorphic behavior by bypassing the vtable

$this:
-$this refers to the current object
-$this can be used to call object functions
-$this should not be used to call static member variables. Use self instead.
-$this can not be used inside static functions

self = Current class.
static = Current class in runtime.
parent = Parent class.

class Test
{
    private $baz = 1;

	public static function foo() 
    { 
        echo "foo\n"; 
    }

  	public function bar()
  	{
    	echo "bar\n";
	    $this->foo();
    	$this::foo();
	    self::foo();
        self::baz();
  	}

	public function baz()
    {
        printf("baz = %d\n", $this->baz);
    }
}

$test = new Test;
$test->bar(); // bar foo foo foo baz = 1 

PHP manual
Declaring class properties or methods as static makes them accessible without needing an instantiation of the class. A property declared as static can not be accessed with an instantiated class object (though a static method can).

Test::foo(); // foo

Is the same as

$test->foo(); // foo