<?php

set_time_limit(0);
echo "<pre>";
$file = "log.txt";
// Pure array no copy
    function m1($file) {
        $fp = fopen($file, "r");
        $size = filesize($file);

        $list = array();
        $n = 0;
        while ( true ) {
            fseek($fp, mt_rand(0, $size));
            fgets($fp);
            $pos = ftell($fp);
            isset($list[$pos]) or $list[$pos] = trim(fgets($fp)) and $n ++;
            if ($n >= 100)
                break;
        }
        return $list;
    }

// Array clean copy
    function m2($file) {
        $lines = file($file);
        shuffle($lines);
        $list = array_slice($lines, 0, 100);
        return $list;
    }

$result = array('m1' => 0,'m2' => 0);

for($i = 0; $i < 1; ++ $i) {
    foreach ( array_keys($result) as $key ) {
        $alpha = microtime(true);
        $key($file);
        $result[$key] += microtime(true) - $alpha;
    }
}

echo '<pre>';
echo "Single Run\n";
print_r($result);
echo '</pre>';

$result = array('m1' => 0,'m2' => 0);

for($i = 0; $i < 2; ++ $i) {
    foreach ( array_keys($result) as $key ) {
        $alpha = microtime(true);
        $key($file);
        $result[$key] += microtime(true) - $alpha;
    }
}

echo '<pre>';
echo "Dual Run\n";
print_r($result);
echo '</pre>';

?>