First off, I tried to write identical code to open a file and perform a regular expression match for a keyword. Here's my resulting code:

open FILE, "<", "haystack_1gig.txt" or die $!;




my $i;


my $search = 'thou';


while (<FILE>) {


        while ($_ =~ s/$search/gi) {


                $i++;


        }


}




print "found $search $i timesn";

<?php


        $file = file("haystack_1gig.txt");


        $search = 'thou';


        $i = 0;


        foreach ($file as $line)


        {


                $i += preg_match_all("/$search/i", $replace, $matches);


        }


        echo "found $search $i timesn";


?>

** A reflection on this code now that I have completed my study is that I believe the file() function in PHP loads the entire contents of the file into memory via the array $file, and thus is more resource intensive than Perl's method, which simple opens a handler to read the file line by line.

After testing the search on a 1 gigabyte, 1 megabyte, 100 kilbyte, and 10 kilobyte files, the results are as follows:

These test times included complete execution time, and thus may not be completely indicative of the pure difference between regular expression computations. However, I wanted to view the difference in the complete process of loading a string and working with it, and thus chose to monitor the complete execution time outside of the script itself.

*Both PHP and Perl optimize data flows (they get faster loading and working with the same data each time), so I ran these scripts multiple times for each filesize, removing the highest and lowest results and averaging the rest.

The next test involved string search and replacement, and thus I made a few simple changes to my code:

	while ($_ =~ s/$search/$replace/gi) {

	preg_replace("/$search/i", $replace, $line, -1, $x);


	$i += $x;

The results for this test:

So in both cases, Perl came out a dominate winner. Although in the more practical examples (filesize of 1 megabyte and smaller) we're talking about microseconds of overall runtime difference, it appears that Perl has the edge over PHP on regular expression operations.