$a = ''; echo '1.-----------'.($a == '').'<br>'; echo '2.-----------'.($a == null).'<br>'; echo '3.-----------'.($a == false).'<br>'; echo '4.-----------'.($a == '0').'<br>'; echo '5.-----------'.($a == 0).'<br>'; $a = null; echo '6.-----------'.($a == '').'<br>'; echo '7.-----------'.($a == null).'<br>'; echo '8.-----------'.($a == false).'<br>'; echo '9.-----------'.($a == '0').'<br>'; echo '10.-----------'.($a == 0).'<br>'; $a = '0'; echo '11.-----------'.($a == '').'<br>'; echo '12.-----------'.($a == null).'<br>'; echo '13.-----------'.($a == false).'<br>'; echo '14.-----------'.($a == '0').'<br>'; echo '15.-----------'.($a == 0).'<br>'; $a = 0; echo '16.-----------'.($a == '').'<br>'; echo '17.-----------'.($a == null).'<br>'; echo '18.-----------'.($a == false).'<br>'; echo '19.-----------'.($a == '0').'<br>'; echo '20.-----------'.($a == 0).'<br>'; $a = false; echo '21.-----------'.($a == '').'<br>'; echo '22.-----------'.($a == null).'<br>'; echo '23.-----------'.($a == false).'<br>'; echo '24.-----------'.($a == '0').'<br>'; echo '25.-----------'.($a == 0).'<br>'; [b]输出的结果 [/b]1.-----------1 2.-----------1 3.-----------1 4.----------- 5.-----------1 6.-----------1 7.-----------1 8.-----------1 9.----------- 10.-----------1 11.----------- 12.----------- 13.-----------1 14.-----------1 15.-----------1 16.-----------1 17.-----------1 18.-----------1 19.-----------1 20.-----------1 21.-----------1 22.-----------1 23.-----------1 24.-----------1 25.-----------1 $a = '';//0|'0'|false|null 输出的结果一致 echo '1.-------'.(!empty($a) == '').'<br>'; echo '2.-------'.(!empty($a) == null).'<br>'; echo '3.-------'.(!empty($a) == false).'<br>'; echo '4.-------'.(!empty($a) == '0').'<br>'; echo '5.-------'.(!empty($a) == 0).'<br>'; [b]输出的结果： [/b]1.-------1 2.-------1 3.-------1 4.-------1 5.-------1