Last updated: Fri, 30 Oct 2009

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.

**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()

Hinweis: 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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Function Overloading Feature

JW
13-Nov-2009 12:11


There are additional overloaded functions, at least in PHP 5.2.8. I'm not sure why they aren't mentioned here.



value of mbstring.func_overload   original function   overloaded function

2                                 stripos             mb_stripos

2                                 strripos            mb_strripos

2                                 strstr              mb_strstr

2                                 strrchr             mb_strrchr

2                                 stristr             mb_stristr

andrew
21-May-2009 09:38


It seems in php 5.2.7 - 5.2.9 under windows mbstring overloading not working in .htaccess files. Apache v.2.2.

Works only in php.ini, this is not convinient in some situations.

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Last updated: Fri, 30 Oct 2009