In daily web development or server management, it is sometimes necessary to ensure that the files uploaded by users are free from viruses or malicious content. Although PHP itself is not an antivirus tool, by combining the md5_file() function with a virus signature database, a simple virus detection mechanism can be implemented. This article will explain how to use PHP's md5_file() function along with a virus database to check if a file is a known virus.

In PHP, the bindec() function is used to convert a binary string into a decimal number. Its basic usage is simple: pass in a pure binary string (made up of 0s and 1s), and it will return the corresponding decimal integer.