Summary

In general, persistent database connections are a very powerful component of PHP. A lot of speed can be gained by "recycling" backend processes, which is very important on high-performance Web sites.

Persistent database connections also have disadvantages. In addition to risks concerning the memory usage of your server, persistent database connections can also be a problem, when dealing with transactions, if your code does not contain a perfect transaction handling system.

It's up to you to decide whether persistent database connections are an advantage for your Web site.