php的静态方法调用有关问题，求大牛解答

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<br />
<?php<br />
class Cat {<br />
}<br />
class Hypnotic_Cat extends Cat {<br />
// Constructor<br />
	function Hypnotic_Cat( ) {<br />
	}<br />
// This function must be called statically<br />
	public static function hypnotize( ) {<br />
		echo ("The cat was hypnotized.");<br />
		//return;<br />
	}<br />
}<br />
// Hypnotize all cats<br />
//Hypnotic_Cat::hypnotize( );<br />
$hypnotic_cat = new Hypnotic_Cat( );<br />
// Does nothing<br />
$hypnotic_cat->hypnotize( );<br />
?><br />