Generally, self is only used to refer to static methods and properties (though confusingly you can refer to non-static methods with self, and to static methods with $this, provided the methods called with self don't reference $this.)
<?php
class Test {
public static function staticFunc() {echo "static ";}
public function nonStaticFunc() {echo "non-static\n";}
public function selfCaller() {self::staticFunc(); self::nonStaticFunc();}
public function thisCaller() {$this->staticFunc(); $this->nonStaticFunc();}
}
$t = new Test;
$t->selfCaller(); // returns "static non-static"
$t->thisCaller(); // also returns "static non-static"
Inheritance is important to remember when dealing with $this or self. $this will always refer to the current object, while self refers to the class in which self was used. Modern PHP also includes late static binding via the static keyword, which will operate the same way as (and should be preferred over) $this for static functions.
<?php
class Person {
public static function whatAmI() {return "Human";}
public function saySelf() {printf("I am %s\n", self::whatAmI());}
public function sayThis() {printf("I am %s\n", $this->whatAmI());}
public function sayStatic() {printf("I am %s\n", static::whatAmI());}
}
class Programmer extends Person {
public static function whatAmI() {return "a programmer";}
}
$p = new Programmer;
$p->saySelf(); // returns "I am Human"
$p->sayThis(); // returns "I am a programmer"
$p->sayStatic(); // returns "I am a programmer"
As regards PHPUnit in particular, it appears they simply do things the way they've always done them! Though according to their documentation, your code should work fine using static methods.
