$a = 'hello'; $$a = 'world'; echo $$a; echo $hello;

$a = 'hello'; $$a = 'world'; echo $$a; echo $hello;
$a = 'hello'; $$a = 'world'; echo $$a; echo $hello;

$a = 'hello'; $$a = 'world'; echo $$a; echo $hello;
这是php比较灵活的地方,因为前面定义了$a='hello',所以$$a就相当于$hello,所以$$a = 'world'就相当于$hello = 'world