Memory leak with PHP 8.1

[3rd3]

It appears that the loaded images remain in memory even when the FastImageSize object is unset.

PHP 8.1.13
Zend Engine v4.1.13
Zend OPcache v8.1.13

Loaded extensions:

zend_extension=opcache.so
extension=pdo.so
extension=pdo_pgsql.so
extension=pgsql.so
extension=xml.so
extension=calendar.so
extension=ctype.so
extension=curl.so
extension=dom.so
extension=exif.so
extension=ffi.so
extension=fileinfo.so
extension=ftp.so
extension=gd.so
extension=gettext.so
extension=iconv.so
extension=imagick.so
extension=intl.so
extension=mbstring.so
extension=phar.so
extension=posix.so
extension=readline.so
extension=shmop.so
extension=simplexml.so
extension=sockets.so
extension=sysvmsg.so
extension=sysvsem.so
extension=sysvshm.so
extension=tokenizer.so
extension=xmlreader.so
extension=xmlwriter.so
extension=xsl.so
extension=zip.so

Code example that demonstrates the leak:

for ($i = 0; $i < ENOUGH_TO_EXCEED_RAM_LIMIT; $i++) {
  $mem = memory_get_usage();
  $FastImageSize = new \FastImageSize\FastImageSize();
  $path = "path/to/image.jpg";
  $imageSize = $FastImageSize->getImageSize($filePath);
  unset($FastImageSize);
  unset($imageSize);
  echo "leak: " . memory_get_usage() - $mem . " bytes<br>";
}

This code terminates with the following fatal error: Allowed memory size of 268435456 bytes exhausted (tried to allocate 790528 bytes) in /var/www/vendor/marc1706/fast-image-size/lib/FastImageSize.php on line 189

[exactmultiple3425]

After checking the code, it is because FastImageSize uses the private property classMap to host TypeBase objects. However, TypeBase objects are constructed with the current FastImageSize, which leads to PHP being unable to perform garbage collection as the reference counting is always greater than 0. If you want to avoid this leak, do not create FastImageSize in a loop; just call the object->getImageSize inside the loop.