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:CopyCodeThe Code is as follows: <? PHP
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 '<H2> isset: </H2> ';
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 '<H2> empty: </H2> ';
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 '<H2> is_numeric: </H2> ';
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 "<H2 >\$ _ Get ['fo'] ='': </H2> ";
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 'male';
} elseif ($ _ Get ['sex'] = 'F') {
echo 'female ';
}< BR >?>
copy the Code the code is as follows:
untitled document
pass valid values pass null values 0
Gender: male gender: female
clear