protected function readValue($key) {
		$data = $this->readData();
		return isset($data[$key]) ? $this->decode($data[$key]) : null;
	}
protected function readValue($key) {
		$data = $this->readData();
		return isset($data[$key]) ? $this->decode($data[$key]) : null;
	}
protected function readValue ( $ key ) { $ data = $ this -> readData ( ) ; return isset ( $ data [ $ key ] ) ? $ this -> decode ( $ data [ $ key ] ) : null ; }
Read value from shm segment
@param string key
@return string | null if field doesn't exist
Read value from shm segment