php 0、null、empty和false之间的关系
2015-01-13 11:35
591 查看
// 判断 0 与 ''、null、empty、false 之间的关系 $a = 0; echo "0 与 ''、 empty、null、false 之间的关系:"; if($a == ''){ echo "0 == '';"; }else{ echo "0 != '';"; } if(trim($a) == ''){ echo "trim(0) == '';"; }else{ echo "trim(0) != '';"; } if(strval($a) == ''){ echo "strval(0) == '';"; }else{ echo "strval(0) != '';"; } if($a === ''){ echo "0 === '';"; }else{ echo "0 !=== '';"; } if(empty($a)){ echo "0 is empty;"; }else{ echo "0 is not empty;"; } if(is_null($a)){ echo "0 is null;"; }else{ echo "0 is not null;"; } if(is_numeric($a)){ echo "0 is numeric;"; }else{ echo "0 is not numeric;"; } if(is_string($a)){ echo "0 is string;"; }else{ echo "0 is not string;"; } if(!$a){ echo "0 is false;"; }else{ echo "0 is not false;"; } // 判断 '' 和 0、null、empty、false 之间的关系 $a = ''; echo "'' 和 0、empty、null、false 之间的关系:"; if($a == 0){ echo "'' == 0;"; }else{ echo "'' != 0;"; } if(intval($a) == 0){ echo "intval('') == 0;"; }else{ echo "intval('') != 0;"; } if(empty($a)){ echo "'' is empty;"; }else{ echo "'' is not empty;"; } if(is_null($a)){ echo "'' is null;"; }else{ echo "'' is not null;"; } if(is_numeric($a)){ echo "'' is numeric;"; }else{ echo "'' is not numeric;"; } if(is_string($a)){ echo "'' is string;"; }else{ echo "'' is not string;"; } if(!$a){ echo "'' is false;"; }else{ echo "'' is not false;"; } // 判断 null 和 ''、0、empty、false 之间的关系 $a = null; echo "null 和 ''、0、empty、false 之间的关系:"; if($a == ''){ echo "null == '';"; }else{ echo "null != '';"; } if($a == 0){ echo "null == 0;"; }else{ echo "null != 0;"; } if($a === ''){ echo "null === '';"; }else{ echo "null !=== '';"; } if($a === 0){ echo "null === 0;"; }else{ echo "null !=== 0;"; } if(strval($a) == ''){ echo "strval(null) == '';"; }else{ echo "strval(null) != '';"; } if(intval($a) == 0){ echo "intval(null) == 0;"; }else{ echo "intval(null) != 0;"; } if(empty($a)){ echo "null is empty;"; }else{ echo "null is not empty;"; } if(is_numeric($a)){ echo "null is numeric;"; }else{ echo "null is not numeric;"; } if(is_string($a)){ echo "null is string;"; }else{ echo "null is not string;"; } if(!$a){ echo "null is false;"; }else{ echo "null is not false;"; } echo "";
运行结果:
0 与 '' empty null false 之间的关系:
0 == '';
trim(0) != '';
strval(0) != '';
0 !=== '';
0 is empty;
0 is not null;
0 is numeric;
0 is not string;
0 is false;
'' 和 0 empty null false 之间的关系:
'' == 0;
intval('') == 0;
'' is empty;
'' is not null;
'' is not numeric;
'' is string;
'' is false;
null 和 '' 0 empty false 之间的关系:
null == '';
null == 0;
null !=== '';
null !=== 0;
strval(null) == '';
intval(null) == 0;
null is empty;
null is not numeric;
null is not string;
null is false;
需要注意的是0,null,false都是empty,
相关文章推荐
- PHP中空字符串介绍0、null、empty和false之间的关系
- PHP中空字符串介绍0、null、empty和false之间的关系
- PHP中空字符串介绍0、null、empty和false之间的关系
- PHP中空字符串介绍0、null、empty和false之间的关系
- PHP中空字符串介绍0、null、empty和false之间的关系
- PHP中空字符串介绍0、null、empty和false之间的关系
- php中0,null,empty,空,false,字符串关系详解
- php中0,null,empty,空,false,字符串关系详解
- php中0,null,empty,空即''与false的关系
- php中0,null,empty,空,false,字符串关系的详细介绍
- php中0,null,empty,空,false,字符串关系的详细介绍
- php 0,null,empty,空,false,字符串关系
- php中0,null,empty,空,false,字符串关系详解
- php 0,null,empty,空,false,字符串关系(转)
- php中0,null,empty,空,false,字符串关系详解
- php中0,null,empty,空,false,字符串关系的详细介绍
- php 0,null,false,empty,isset详解
- 有关JS中的0,null,undefined,[],{},'''''''',false之间的关系
- 类型串php中null和false和0之间的区别
- php中empty(),is_null(),isset(),bool之间的区别