Benchmark One - High
4.48800283 - 4000 cycles
Benchmark Two - High
3.24294379 - 4000 cycles
Benchmark One - Low
5.17224769 - 4000 cycles
Benchmark Two - Low
4.31859057 - 4000 cycles
Current Benchmark
<?php
$find = 'syridium';
$replace = 'ME!';
$string = $str;
echo strtr($string, array($find => $replace));
?>
vs.
<?php
$find = 'syridium';
$replace = 'ME!';
$string = $str;
echo str_replace($find, $replace, $string);
?>
Conclusion
After an average of 4000 cycles, the fastest option is Benchmark 2!
<?php
$find = 'syridium';
$replace = 'ME!';
$string = $str;
echo str_replace($find, $replace, $string);
?>