Share the usage of the three functions ISSET (), empty (), and is_numeric () in PHP form verification. For more information about php learning, see. 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:
The code is as follows:
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 {
Echo 'isset of variable/'Fo/'is false and 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.
Echo 'is_numeric of the variable/'Fo/'is true, a number ';
} Else {
The 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 ';
}
?>
Untitled Document
Pass a valid value to pass a null value to 0
Gender: Male Gender: Female
Clear
