php tmpdir() alternative to tmpfile()

Question

tmpfile() creates a temporary file which is automatically deleted when php exit. I wanted the same for directories, came up with:

/**
 * create a temporary directory that is automatically deleted when the script exits.
 * 
 * @throws RuntimeException on tmpfile()/mkdir() failure
 * @return string absolute path to the temporary directory
 */
function tmpdir(): string
{
 $max_attempts = 10;
 $attempts = 0;
 for (; $attempts < $max_attempts; ++$attempts) {
 $h = tmpfile();
 if ($h === false) {
 continue;
 }
 $tmpDirPath = stream_get_meta_data($h)['uri'];
 fclose($h);
 // there is technically a (unlikely) race condition between fclose() and mkdir(),
 // that's why i do the weird loop thing
 if (mkdir($tmpDirPath)) {
 break;
 }
 }
 if ($attempts >= $max_attempts) {
 throw new RuntimeException("tmpdir() failed: attempts: " . $attempts . ": error_get_last: " . var_export(error_get_last(), true));
 }
 static $deleteOnExitInstalled = false;
 static $tmpDirPaths = [];
 $tmpDirPaths[] = $tmpDirPath;
 if ($deleteOnExitInstalled === false) {
 register_shutdown_function(function () use (&$tmpDirPaths) {
 $rmdirRecursively = function ($dir) use (&$rmdirRecursively) {
 $children = glob($dir . DIRECTORY_SEPARATOR . '*', GLOB_NOSORT | GLOB_MARK);
 foreach ($children as $child) {
 $isChildDir = substr($child, -strlen(DIRECTORY_SEPARATOR)) === DIRECTORY_SEPARATOR;
 if ($isChildDir) {
 $rmdirRecursively(substr($child, 0, -strlen(DIRECTORY_SEPARATOR)));
 } else {
 unlink($child);
 }
 }
 rmdir($dir);
 };
 foreach ($tmpDirPaths as $tmpDirPath) {
 $rmdirRecursively($tmpDirPath);
 }
 });
 $deleteOnExitInstalled = true;
 }
 return $tmpDirPath;
}

sample usage:

$tmpDir = tmpdir();
file_put_contents("{$tmpDir}/test.txt", "Hello World!");
var_dump($tmpDir); // /tmp/phpSyEj2v

• KIKO Software: Can you explain why you want to create a temporary directory? All it could possibly contain are temporary files, but those you can already make. In other words: I am wondering if this is best solution for the problem you're trying to solve, but I don't know what that problem is.
• hanshenrik: @KIKOSoftware I want a temporary directory for a headless Chrome's --user-data-dir argument
• KIKO Software: OK, I get it. One thing I would do is make deleting a non-empty directory a separate function. It could be useful to a have a function like that, and not have to write one again.
• mickmackusa: I see how you are using static with $deleteOnExitInstalled to control its boolean value after subsequent calls of tmpdir(). Does $tmpDirPaths need this same behavior? It cannot start from scratch each time? Why not put $attempts = 0; in the first parameter of for()? Why not make $max_attempts = 10 the default parameter of tmpdir() to make it more easily customizable? Trivially, I'd use sprintf() with the runtimeException messge to manage the code line length. I might also cache the strlen() of the DS.
• hanshenrik: @mickmackusa Does $tmpDirPaths need this same behavior? It cannot start from scratch each time? - yes, the shutdown function use this array to keep track of all the temporary directories created. Why not put $attempts = 0; in the first parameter of for()? - in PHP it doesn't really matter, but in many other languages (javascript, C, C++, Rust, just off the top of my head) , variables created in the for loop, goes out of scope outside the for loop, so i have a habit of declaring variables used outside for loops, outside the for loop. (even though it's not required in PHP)

Answer 1

Found at least 1 bug: if the file contains symlinks, then

$isChildDir = substr($child, -strlen(DIRECTORY_SEPARATOR)) === DIRECTORY_SEPARATOR;

will incorrectly be true, resulting in the dir not being cleaned up and emitting

PHP Warning: rmdir(/tmp/phpOuCtAg/symlink): Not a directory in foo.php on line x

The fix seems to be

 foreach ($children as $child) {
 $isChildDir = substr($child, -strlen(DIRECTORY_SEPARATOR)) === DIRECTORY_SEPARATOR;
 if ($isChildDir) {
 $withoutTrailingSlash = substr($child, 0, -strlen(DIRECTORY_SEPARATOR));
 if (is_link($withoutTrailingSlash)) {
 unlink($withoutTrailingSlash);
 } else {
 $rmdirRecursively($withoutTrailingSlash);
 }
 } else {
 unlink($child);
 }
 }

I think that could probably be shortened further.