Function Overloading Feature
You might often find it difficult to get an existing PHP
application work in a given multibyte environment. That's
mostly because lots of 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 '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 the 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 is set for 7, mail, strings and
regular expression functions should be overloaded. The list
of overloaded functions are shown below.
Table 2. Functions to be overloaded
value of mbstring.func_overload original function overloaded
function
1 mail() mb_send_mail()
2 strlen() mb_strlen()
2 strpos() mb_strpos()
2 strrpos() mb_strrpos()
2 substr() mb_substr()
2 strtolower() mb_strtolower()
2 strtoupper() mb_strtoupper()
2 substr_count() mb_substr_count()
4 ereg() mb_ereg()
4 eregi() mb_eregi()
4 ereg_replace() mb_ereg_replace()
4 eregi_replace() mb_eregi_replace()
4 split() mb_split()
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.
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