This function uses the PHP crc32 function:
From php.net:
crc32(): Calculates the crc32 polynomial of a string

Information from Wikkipedia the the free encyclopedia.:

A cyclic redundancy check (CRC) is a type of hash function used to produce a checksum - which is a small number of bits - against a byte or a larger block of data, such as a packet of network traffic or a block of a computer file. The checksum is used to detect and correct errors after transmission or storage. A CRC is computed and appended before transmission or storage, and verified afterwards by recipient to confirm that no changes occurred on transit. Correction can also be done if information lost is lower than information held by the checksum. CRCs are popular because they are simple to implement in binary hardware, are easy to analyze mathematically, and are particularly good at detecting common errors caused by noise in transmission channels.