PHP 8.0: Disabled functions: Reflection and get_defined_functions() deprecations


In PHP 8, disabled functions are not added to PHP's internal functions table. This makes PHP behave as if disabled functions are not defined at all.

Related to this change, there are two new deprecations in PHP 8.

ReflectionFunction::isDisabled() is deprecated

ReflectionFunction::isDisabled() method is deprecated because it no longer provides any useful information to the caller.

Deprecated: Function ReflectionFunction::isDisabled() is deprecated in %s on line %d

This method will always return false even if the function is disabled with the INI directive.

There is no need to check if a function is disabled because function_exists() will return true only if the function is declared and not disabled.

get_defined_functions($exclude_disabled = false) is deprecated

For the same reasons that disabled functions are not included in functions list, get_defined_functions() function with the first parameter $exclude_disabled set to false is disabled.

get_defined_functions() will always exclude disabled functions in PHP 8, and even if you try to get all functions including the excluded ones, it will not return disabled functions.

If you redefine a disabled function, that function will be in the user key of the get_defined_functions() return array, even if it is defined internally and disabled via the disable_functions INI directive.

Backwards compatibility impact

The main use-case for disable_functions INI directive is to disable potentially unsafe functions such as system(). The deprecation notices are unlikely to occur, but it does not introduce any loss of functionality.

A fuzzy GitHub code search does not yield any uses this pattern.