php中isset和empty区别

http://seawomen.iteye.com/blog/629786

?

＄id=0;empty(＄id)?print "It's empty .":print "It's ＄id ."; //结果：It's empty .print "<br>";!isset(＄id)?print "It's empty .":print "It's ＄id .";//结果：It's 0 .
if(empty(＄id)) ＄id=1; //若 id=0 ，id 也会为1if(!isset(＄id)) ＄id=1; // 若 id=0 ，id 不会为1
if(emptyempty(＄id))?＄id=1; ??print?＄id;?//?得到?1 ??if(!isset(＄id))?＄id=1; ??print?＄id;?//得到?0??