code: public function nextkey() {
  		if ( $this->keyIterPos >= $this->keyIterStop ) {
  			return false;
  		}
  		$keyLen = $this->readInt31( $this->keyIterPos );
  		$dataLen = $this->readInt31( $this->keyIterPos + 4 );
  		$key = $this->read( $this->keyIterPos + 8, $keyLen );
  		$this->keyIterPos += 8 + $keyLen + $dataLen;
  
  		return $key;
  	}
docs: Get the next key from the CDB file.
  
  @return string|bool Key, or false if no more keys.