Function Overloading Feature
You might often find it difficult to get an existing PHP application
to work in a given multibyte environment. This happens because most
PHP applications out there are written with the standard string
functions such as substr(), which are known to
not properly handle multibyte-encoded strings.
mbstring supports a 'function overloading' feature which enables
you to add multibyte awareness to such an application without
code modification by overloading multibyte counterparts on
the standard string functions. For example,
mb_substr() is called instead of
substr() if function overloading is enabled.
This feature makes it easy to port applications that only support
single-byte encodings to a multibyte environment in many cases.
To use function overloading, set
mbstring.func_overload in php.ini to a
positive value that represents a combination of bitmasks specifying
the categories of functions to be overloaded. It should be set
to 1 to overload the mail() function. 2 for string
functions, 4 for regular expression functions. For example,
if it is set to 7, mail, strings and regular expression functions will
be overloaded. The list of overloaded functions are shown below.
Note:
It is not recommended to use the function overloading option in
the per-directory context, because it's not confirmed yet to be
stable enough in a production environment and may lead to undefined
behaviour.
