Returns the value of the header or null if not found.

@param string $name The name of the header.
@return string|null The value of the header requested of null if not found.
557712
public function getValue(string $name): ?string
    {
        if (isset($this->data[$name])) {
            return $this->data[$name]->value;
        }
        return null;
    }
674580
@Nullable
    public String getHeader(String name) {
        requireNonNull(name);
        List<String> values = lazyMap.get().get(name.toLowerCase());
        if (values == null) {
            return null;
        }
        return values.get(0);
    }
936678
protected function get(string $name)
    {
        $name[0] = strtolower($name[0]);

        return $this->list[$name] ?? null;
    }
523588
public function getGet($name = null)
    {
        if ($name !== null) {
            return isset($this->getParams[$name]) ? $this->getParams[$name] : null;
        }

        return $this->getParams;
    }
65401
public function getValue($name = 'key')
    {
        if (!isset($this->rawData[$name])) {
            return null;
        }

        return $this->rawData[$name];
    }
107318
public function getHeader(string $name)
    {
        $name = strtolower($name);
        foreach ($this->headers as $current => $value) {
            if (strtolower($current) == $name) {
                return $value;
            }
        }

        return null;
    }
323982
public function getValue($name)
    {
        if (! is_string($name)) {
            return null;
        }

        $bits = explode('.', $name);
        $postData = $_POST;

        foreach ($bits as $key) {
            if (is_array($postData) && isset($postData[$key])) {
                $postData = $postData[$key];
            } else {
                return null;
            }
        }

        return $postData;
    }
852500
public function getOriginalHeader($name)
    {
        return array_key_exists($name, $this->_request)? $this->_request[$name]: null;
    }
356119
public function get(string $name)
    {
        if ($this->has($name)) {
            return $this->values[$name];
        } else {
            return $this->throwNotFound($name);
        }
    }
367742
public static function get(string $name): ?string
    {
        $data = Session::get($name, null, self::$namespace);
        if (is_array($data) && array_key_exists('token', $data)) {
            return $data['token'];
        }
        return null;
    }
1047444
public function get($name)
    {
        return isset($this->value[$name])
            ? $this->value[$name]
            : null;
    }
214120
public function getHeaders(string $name = null)
    {
        if (is_null($name)) {
            return $this->get('headers');
        }

        return $this->get('headers', $name);
    }
950682
public function getByName($name)
    {
        return isset($this->names[$name]) ? $this->names[$name] : null;
    }
106288
public static function get($name)
    {
        $name = ltrim($name, '\\');
        if (!$data = self::getInternal($name)) {
            return null;
        }

        return $data;
    }
1065938
public function getHeaderValue($key)
    {
        return isset($this->headers[$key]) ? $this->headers[$key] : null;
    }
1174875
private function getHeader($name)
    {
        if (isset($this->headers[$name])) {
            return $this->headers[$name];
        }
        return false;
    }
270906
public function header($name)
    {
        $exists = isset($this->headers[$name]);

        return $exists ? $this->headers[$name] : array();

        // getHeader
    }