Can classes in PHP judge the received parameters?

Question

classInput.php
<?php
header("Content-Type:text/html; charset=UTF-8");
classInput{
    function post($key){
                $val=$_POST[$key];
                return $val;
    }
}
?>

save.php
<?php
header("Content-Type:text/html; charset=UTF-8");
include 'classInput.php';
$input=new Input();
$userName=$input->post('userName');
$msg=$input->post('msg');

Then I accessed save.php directly and reported a notice error. Can I judge the passed parameters in classInput.php?

Answer 1

header("Content-Type:text/html; charset=UTF-8");
class Input{
    function post($key){
                if( isset($_POST[$key]))
                    $val=$_POST[$key];
                else
                    $val=null;
                return $val;
    }
}

Answer 2

<?php
header("Content-Type:text/html; charset=UTF-8");
class Input{
    function post($key){
        if(isset($_POST[$key])){
                $val=$_POST[$key];
                return $val;
        }
    }
}
?>

Answer 3

First, determine whether it is a post request. If it is a post request, then determine whether the value exists.

Answer 4

Made some modifications to your class

<?php
class Input{
    var $_Get='';
    var $_Post='';
    function __construct($data){
        print_r($data);
        $this->_Get  = $data['get'];
        $this->_Post = $data['post'];
    }
    function post($key){
        $data = $this->_Get;
        $val  = $data[$key];
        return $val;
    }
}

//然后调用的时候
include 'classInput.php';
$input=new Input(['get'=>$_GET]);
$userName=$input->post('userName');
echo $userName;
//这样就好了把