While working on an application I ran across a huge bottleneck which I isolated down all the way to the use of the iconv_substr function. If you ever wonder which is better to use, [the benchmark code in the post[ should help your decision.

His results changed quite a bit from machine to machine (and OS/platform to OS/platform) but one statistic stood out on them all - the iconv_substr was slower than mb_substr method....by a lot in one case (about 2100000% slower).