Definition and scope of action: used to test whether a variable has a value (including 0, FALSE, or an empty string, but cannot be NULL), that is, "http: // localhost /? Fo "can also pass detection, so it is not applicable. However, the "http: // localhost/" parameter does not include
ISSET (); -- this parameter is suitable for detecting whether this parameter exists.
Definition and scope of action: used to test whether a variable has a value (including 0, FALSE, or an empty string, but cannot be NULL), that is, "http: // localhost /? Fo = "can also pass detection, so it is not applicable. However, if the "http: // localhost/" parameter does not contain the fo parameter, you can use isset for detection. in this case, isset ($ _ GET ['fo']) returns false.
Not applicable: This function is not suitable for verifying text in html forms. To check whether the user input text is valid, you can use empty ();
Empty (); -- the best function.
Definition and scope of action: used to check whether a variable has a null value, including: null string, 0, null, or false, that is, "http: // localhost /? Fo = "or" http: // localhost /? When fo = 0 ", empty detects true and does not apply to values: 0.
Is_numeric (); -- this parameter is only applicable to the detection of numbers. if the parameter name does not exist, an error occurs. Therefore, it is not suitable for the first-level detection.
Comprehensive example:
Ini_set ("display_errors", 1 ); // Ini_set ("error_reporting", E_ALL); print_r Error_reporting (E_ALL );
$ A = NULL; If (isset ($ a) echo 'isset of variable $ A' is true ';
Echo 'isset :'; If (isset ($ _ GET ['fo']) { Echo 'isset of variable \ 'fo \ 'is true and the variable is usable '; } Else { The isset of echo 'variable \ 'fo \ 'is false and has no variable settings '; }
Echo 'empty :'; If (empty ($ _ GET ['fo']) { Echo 'empty of variable \ 'fo \ 'is true, that is, null or invalid value '; } Else { The empty of echo 'variable \ 'fo \ 'is false and has a value '; }
Echo 'is _ numeric :'; If (is_numeric ($ _ GET ['fo']) {// if the parameter does not contain the fo parameter, an error occurs. The is_numeric of echo 'variable \ 'fo \ 'is true, a number '; } Else { Is_numeric of echo 'variable \ 'fo \ 'is false, not a number '; }
Echo "\ $ _ GET ['fo'] = :"; If ($ _ GET ['fo'] = '') {// if the parameter does not contain the fo parameter, an error occurs. Echo 'Fo no value, empty string '; } Elseif ($ _ GET ['fo']! = ''){ Echo 'Fo has a value, not \'\'.'; }
Echo "\ $ _ GET ['sex'] ='m :"; If ($ _ GET ['Sex '] = 'm') {// an error occurs when no sex variable exists in the parameter. Echo 'mal '; } Elseif ($ _ GET ['sex'] = 'F '){ Echo 'femal '; } ?> |
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Pass a valid value to pass a null value to 0
Gender: Male Gender: Female
Clear
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