PHP md5() Function - W3Schools
The md5 () function calculates the MD5 hash of a string. The md5 () function uses the RSA Data Security, Inc. MD5 Message-Digest Algorithm. From RFC 1321 - The MD5 Message-Digest Algorithm: "The MD5 message-digest algorithm takes as input a message of arbitrary length and produces as output a 128-bit "fingerprint" or "message digest" of the input.