PHP filter_input(INPUT_SERVER, 'REQUEST_METHOD') returns null?

Question

Why does this line return null in my live server?

filter_input(INPUT_SERVER, 'REQUEST_METHOD');

The live server is php5.5.9

Have I missed something?

I thought it is used to replace the global method below?

$_SERVER['REQUEST_METHOD'];

some of the code,

public function __construct()
    {
        // Construct other generic data.
        $this->clientRequestMethod = filter_input(INPUT_GET, 'method'); // such as list, add, update, etc
        $this->clientPostMethod = filter_input(INPUT_POST, 'method'); // such as update
        $this->serverRequestMethod = filter_input(INPUT_SERVER, 'REQUEST_METHOD'); //such as get or post
    }


    public function processEntry()
    {

        // Determine the $_SERVER['REQUEST_METHOD'] whether it is post or get.
        if ($this->serverRequestMethod === 'POST' && $this->clientPostMethod != null) 
        {
            $this->processPost();
        }
        else if($this->serverRequestMethod === 'GET' && $this->clientRequestMethod != null) 
        {
            $this->processRequest();
        }
    }

Answer 1

So the problem/bug is this:

filter_input() doesn't work with INPUT_SERVER or INPUT_ENV when you use FASTCGI

The bug has been known for years and I found nothing saying it was addressed. I found several work-arounds but no complete solution so I plopped the best work-around into this helper function for a project-wide solution. To provide some level of security and avoid train wrecks, the function falls back to filter_var() where filter_input() fails. It uses the same format as the native filter_input() function for easy integration into projects and easy future removal should the bug ever be fixed.

function filter_input_fix ($type, $variable_name, $filter = FILTER_DEFAULT, $options = NULL )
{
    $checkTypes =[
        INPUT_GET,
        INPUT_POST,
        INPUT_COOKIE
    ];

    if ($options === NULL) {
        // No idea if this should be here or not
        // Maybe someone could let me know if this should be removed?
        $options = FILTER_NULL_ON_FAILURE;
    }

    if (in_array($type, $checkTypes) || filter_has_var($type, $variable_name)) {
        return filter_input($type, $variable_name, $filter, $options);
    } else if ($type == INPUT_SERVER && isset($_SERVER[$variable_name])) {
        return filter_var($_SERVER[$variable_name], $filter, $options);
    } else if ($type == INPUT_ENV && isset($_ENV[$variable_name])) {
        return filter_var($_ENV[$variable_name], $filter, $options);
    } else {
        return NULL;
    }
}

This seems the best solution. Please let me know if it contains errors that might cause issues.