Question

I have strong reason to believe that both functions rename() and unlink() are asynchronous, which, from my understanding, means that when the functions are called, the code below them are continued before it finishes its procedures on the filesystem. This is a problem for the internet app I’ll explain below, because later code depends on these changes to already be set in stone. So, is there a way to make both synchronous, so that the code reader freezes when it hits these functions, until all of its tasks are fully carried out on the filesystem?

Here is the code in delete-image.php, which is called by ajax from another admin-images.php(the latter will not be shown):

`

    foreach ($dirScan as $key => $value) {
        $fileParts = explode('.', $dirScan[$key]);
        if (isset($fileParts[1])) {
            if ((!($fileParts[1] == "gif") && !($fileParts[1] == "jpg")) && (!($fileParts[1] == "png") && !($fileParts[1] == "jpg"))) {
                unset($dirScan[$key]);
            }
        } else {
            unset($dirScan[$key]);
        }
    }
    $dirScan = array_values($dirScan);

    // for thumbnail
    $file = 'galleries/' . $currentGal . '/' . $currentDir . "/" . $dirScan[$imageNum - 1];
    unlink($file);      
    for ($i = ($imageNum - 1) + 1; $i < count($dirScan); $i++) {
        $thisFile = 'galleries/' . $currentGal . '/' . $currentDir . '/' . $dirScan[$i];
        $thisSplitFileName = explode('.', $dirScan[$i]);
        $newName = 'galleries/' . $currentGal . '/' . $currentDir . "/" . ($thisSplitFileName[0] - 1)  . "." . $thisSplitFileName[1];
        rename($thisFile, $newName);
    }

    // for large image
    $fileParts = explode('.', $dirScan[$imageNum - 1]);
    $file = 'galleries/' . $currentGal . '/' . $currentDir . "/large/" . $fileParts[0] . "Large." . $fileParts[1];
    unlink($file);
    for ($i = ($imageNum - 1) + 1; $i < count($dirScan); $i++) {
        $thisSplitFileName = explode('.', $dirScan[$i]);
        $thisFile = 'galleries/' . $currentGal . '/' . $currentDir . '/large/' . $thisSplitFileName[0] . "Large." . $thisSplitFileName[1];
        $newName = 'galleries/' . $currentGal . '/' . $currentDir . "/large/" . ($thisSplitFileName[0] - 1)  . "Large." . $thisSplitFileName[1];
        rename($thisFile, $newName);
    }

    sleep(1);
    echo 'deleted ' . $dirScan[$imageNum - 1] . " successfully!";

} else {
    echo "please set the post data";
} ?>`

After this script returns its completed text, admin-images.php triggers a new function which populates an image table from these renamed and trimmed files. Sometimes it displays old names and files that were suppose to be deleted, and a simple page refresh gets rid of them. This seems to suggest that the above php script is running through all the code and spitting out echoed text to the mainfile before it completes its file-system manipulation (All of this other code is long and complicated, and hopefully unnecessary for the discussion at hand).

You’ll notice, I’ve tried a sleep() function to halt the php script to hopefully give it time to finish. This is an ineligent, and problematic way of doing things, because I have to put a large amount of time to insure it works every-time, but I don’t want the user to wait longer than she / he has to.

Answer 1

I suppose they are not asynchronous, because they return a result telling if the operation was successful or not.

I believe the problem happens because when you run scandir after making the modifications, it may be using “cached” data, from memory, instead of re-scanning the file system.