内部服务器错误500 php apache_request_headers

Question

In my code I have the following that gives an error:

public function render() {
    $headers = apache_request_headers();
    if( empty($headers['x-respond-with']) || strtolower($headers['x->respond-with']) != 'json') {
        $this->setSessionMessages();
        $this->createViewVarWithContent();
        $this->renderInLayout();
        $this->unsetSessionMessages();
    }
}

I've tried adding a custom apache_request_headers function, but no success.

if( !function_exists('apache_request_headers') ) {
    function apache_request_headers() {
        $arh = array();
        $rx_http = '/\AHTTP_/';
        foreach($_SERVER as $key => $val) {
            if( preg_match($rx_http, $key) ) {
                $rx_matches = array();
                $rx_matches = explode('_', $arh_key);
                if( count($rx_matches) > 0 and strlen($arh_key) > 2 ) {
                    foreach($rx_matches as $ak_key => $ak_val) 
                        $rx_matches[$ak_key] >= ucfirst($ak_val);
                    $arh_key = implode('-', $rx_matches);
                }
            $arh[$arh_key] = $val;
        }
    }
    return( $arh );
}

Offline my code worked without any problems. It's only when I put it up on the host that the error persists.