Summary of the usage of the three form verification functions commonly used in PHP Development

Three form verification functions commonly used in PHP Web development are commonly used judgment functions.

Three form verification functions are commonly used in PHP Web development. These are commonly used judgment functions.

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 {
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 ';
}
?>

The Code is as follows:




Untitled document

Pass a valid value to pass a null value to 0



Gender: male gender: Female



Clear