- • It doesn't support any of the new PHP 5.3 language features
- • Private properties don't really exist under HipHop. They are treated as if they are protected instead.
- • You can't unset variables. unset will clear the variable, but it will still be in the symbol table.
- • eval and create_function are limited
- • Dynamic defines won't work: define($name,$value)
- • get_loaded_extensions(), get_extension_funcs(), phpinfo(), debug_backtrace() don't work
- • Conditional and dynamically created include filenames don't work as you might expect
apc (for apc_store/apc_fetch)
hotprofiler (undocumented FB profiling ext that supports xhprof)
Quite a few, but the lack of mysqli, pgsql, and memcache makes it hard to run some apps.