Physical-layer security is emerging approach that can benefit conventional encryption methods. The main idea of physical layer security is to take advantage of the features of the wireless channel and its impairments in order to ensure secure communication in the physical layer. This paper provides a comprehensive review of information-theoretic measures of the secrecy performance in physical layer security. In addition, our work survey research about physical layer security over several enabling 5G technologies, such as massive multiple-input multiple-output, millimeter wave communications, heterogeneous networks, and full-duplex, including the key concepts of each of the aforementioned technologies. Finally, future research directions and technical challenges of physical layer security are identified.