require vs. require_once

[phpfrizzeak]

My benchmarks from require vs. require_once show require_once to be margianally faster even though it performs an lstat()-like call (puzzling).  What could I be doing wrong?  I am pretty sure APC is DISABLED, but even if it were not what gives?:

 

#!/usr/bin/php
<?php

    $fileNamesRequireOnce = array();
    $fileNamesRequire = array();
    for($i=0; $i<1000; $i++) {
        $fileName = dirname(__FILE__) . '/_test_file_' . $i . ".php";

        if ($i%2 == 0) {
            $fileNamesRequireOnce[] = $fileName;
        } else {
            $fileNamesRequire[] = $fileName;
        }

        $fileHandler = fopen($fileName, 'w');
        fwrite($fileHandler, "<?php class TestClass_" . $i . " { /* ... */ } ?>\n");
        fclose($fileHandler);
    }
    $fileNames = array_merge($fileNamesRequire, $fileNamesRequireOnce);

    $timeStart = microtime(true);
    foreach ($fileNamesRequireOnce as $fileName) {
        require_once($fileName);
    }
    $timeStop = microtime(true);
    $rUsage = getrusage();
    $userTime = $rUsage["ru_utime.tv_usec"]/1e6;
    echo "require_once x" . (count($fileNamesRequireOnce)) . " [" . ($timeStop - $timeStart) . "] with user time [" . $userTime . "]\n";

    $timeStart = microtime(true);
    foreach ($fileNamesRequire as $fileName) {
        require($fileName);
    }
    $timeStop = microtime(true);
    $rUsage = getrusage();
    $userTime = $rUsage["ru_utime.tv_usec"]/1e6;
    echo "require x" . (count($fileNamesRequire)) . " [" . ($timeStop - $timeStart) . "] with user time [" . $userTime . "]\n";

    foreach($fileNames as $fileName) {
        unlink($fileName);
    }

 

Results are as follows:

require_once x500 [0.3516731262207] with user time [0.067989]
require x500 [0.3381929397583] with user time [0.092985]

[phpfrizzeak]

Ooops... looked at the numbers and see a SLIGHT difference in favor of require... I still do not understand where there are no sharp distinctions (even if I dramatically increase the number of included files).

[Maq]

From the manual:

 

The require_once() statement is identical to require() except PHP will check if the file has already been included, and if so, not include (require) it again.

 

There you go, require_once() does an extra check to see if the file has already been included.