Multi-Sandbox Lua Engine (MSLE) is a modified Lua interpreter which supports creation and maintenance of multiple "100% tight" sandboxes from within Lua. "100% tight" means that the amount of memory used by a sandbox (counting both code and data) is strictly limited, a feature Lua did not offer before.
RainCaptcha is a CAPTCHA class that does not require any image processing extensions (GD, ImageMagick, etc). CAPTCHA was developed to be readable by humans and resistant to OCR software. It generates black-and-white images with 5 distorted letters on them and noise. Its checking algorithm is case-insensitive.
ExternalSort is a class that can sort large files similar to the Unix sort command. It can read the file to be sorted in small buckets associated with temporary files to not exceed the configured PHP memory limits. The buckets are sorted individually and then merged to produce the final sorted output. The class provides command line interface options so it can be executed as a command from a shell.