runkit – changing the PHP internals on the fly

Here is something I didn’t know about until today – PHP’s runkit extension:

The runkit extension provides means to modify constants, user-defined functions, and user-defined classes. It also provides for custom superglobal variables and embeddable sub-interpreters via sandboxing.

This blog post – “Shimming PHP for Fun and Profit” – demonstrates how to use it with a case for a custom base64_decode() and unserialize() functions.  Here is the actual code on GitHub, which shows off how to use runkit_function_rename() and runkit_function_add().

This is not something one would use frequently, but might be an absolute life saver on a rainy day.

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