$identifier = md5($content->usercontent);
The md5() function is used here to calculate a fixed-length 32-character hexadecimal hash based on the content stored in $content->usercontent. This hash is essentially a unique fingerprint for the content. If two sets of content have the same exact content, they will produce the same MD5 hash.
To identify duplicates, you can store these MD5 hashes in a database or an array and check if a new content’s hash already exists in that storage. If it does, then you have encountered a duplicate because the same content produces the same hash.