<?php

$str = str_repeat("foo",100000);
$time = microtime(true);

iconv_substr($str,1000,90000,'UTF-8');

echo "iconv_substr: " . (microtime(true)-$time) . "\n";

$time = microtime(true);

mb_substr($str,1000,90000,'UTF-8');

echo "mb_substr: " . (microtime(true)-$time) . "\n";

$time = microtime(true);

substr($str,1000,90000);

echo "substr: " . (microtime(true)-$time) . "\n";
?>