PHP中空字符串、0、null、empty、和false之间的关系.docx

2、se{echo"strval(0)!=''";}echo"
";if($a===''){echo"0===''";}else{echo"0!===''";}echo"
";if(empty($a)){echo"0isempty";}else{echo"0isnotempty";}echo"
";if(is_null($a)){echo"0isnull";}else{echo"0isnotnull";}echo"
";if(is_numeric($a)){echo"0isnumeric";}else{echo"0isnotnumeric";}echo"<

3、br>";if(is_string($a)){echo"0isstring";}else{echo"0isnotstring";}echo"
";if(!$a){echo"0isfalse";}else{echo"0isnotfalse";}echo"
";echo"
";echo'--------------------';?>

4、val($a)==0){echo"intval('')==0";}else{echo"intval('')!=0";}echo"
";if(empty($a)){echo"''isempty";}else{echo"''isnotempty";}echo"
";if(is_null($a)){echo"''isnull";}else{echo"''isnotnull";}echo"
";if(is_numeric($a)){echo"''isnumeric";}else{echo"''isnotnumeric";}echo"
";if(is_strin

5、g($a)){echo"''isstring";}else{echo"''isnotstring";}echo"
";if(!$a){echo"''isfalse";}else{echo"''isnotfalse";}echo"
";echo"
";echo"
";echo"
";echo'--------------------';?>

6、;}echo"
";if($a==0){echo"null==0";}else{echo"null!=0";}echo"
";if($a===''){echo"null===''";}else{echo"null!===''";}echo"
";if($a===0){echo"null===0";}else{echo"null!===0";}echo"
";if(strval($a)==''){echo"strval(null)==''";}else{echo"strval(null)!=''";}echo"
";if(intval($a)==0

7、){echo"intval(null)==0";}else{echo"intval(null)!=0";}echo"
";if(empty($a)){echo"nullisempty";}else{echo"nullisnotempty";}echo"
";if(is_numeric($a)){echo"nullisnumeric";}else{echo"nullisnotnumeric";}echo"
";if(is_string($a)){echo"nullisstring";}e