iconv_substr vs mbstring_substr

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, this should help your decision:

Benchmark script

2. A 
3. $str = str_repeat("foo",100000);
4. $time = microtime(true);
5. A 
6. iconv_substr($str,1000,90000,'UTF-8');
7. A 
8. echo "iconv_substr: " . (microtime(true)-$time) . "\n";
9. A 
10. $time = microtime(true);
11. A 
12. mb_substr($str,1000,90000,'UTF-8');
13. A 
14. echo "mb_substr: " . (microtime(true)-$time) . "\n";
15. A 
16. $time = microtime(true);
17. A 
18. substr($str,1000,90000);
19. A 
20. echo "substr: " . (microtime(true)-$time) . "\n";
21. ?

The results widely varied between machines, operating systems and PHP versions; but here are two results I recorded.

First, PHP 5.3.4 on OS/X:

1. iconv_substr: 0.014400005340576
2. mb_substr: 0.00049901008605957
3. substr: 3.7193298339844E-5 "/

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