This issue was opened previously and closed without resolution two and a half years ago due to lack of feedback in bug #6608. I made a comment there but I'm not sure if closed topics are seen, so I'm opening it here. I apologize if I shouldnt have opened a new bug report.

I'm running on OSX with PHP 4.3.0. The performance with a large array that uses sizeof() in a loop is very poor. It's abut 50X slower than it should be.

The following takes 8-10 seconds:
for ($i=1;$i<=sizeof($spell);$i++) {
     $sentence=str_replace($spell[$i][0],$spell[$i][1],$sentence); 
}

Whereas the following takes only .18 seconds:
$end=sizeof($spell);
for ($i=1;$i<=$end;$i++) {
     $sentence=str_replace($spell[$i][0],$spell[$i][1],$sentence); 
}

Other notes that might help: the array is stored in a file accessed by require_once(), and the loop is in a function that brings $spell in as a global variable.