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PHP : Function Reference : GNU Recode Functions

GNU Recode Functions


This module contains an interface to the GNU Recode library. The GNU Recode library converts files between various coded character sets and surface encodings. When this cannot be achieved exactly, it may get rid of the offending characters or fall back on approximations. The library recognises or produces nearly 150 different character sets and is able to convert files between almost any pair. Most RFC 1345 character sets are supported.


This extension is not available on Windows platforms.


You must have GNU Recode 3.5 or higher installed on your system. You can download the package from


The Recode library version 3.6 adds weird characters behind converted strings under certain circumstances. Thus it's safer to use Recode v3.5 or one of the available alternatives like the iconv or mbstring extension.


To be able to use the functions defined in this module you must compile your PHP interpreter using the --with-recode[=DIR] option.


Crashes and startup problems of PHP may be encountered when loading the recode as extension after loading any extension of mysql or imap. Loading the recode before those extension has proved to fix the problem. This is due a technical problem that both the c-client library used by imap and recode have their own hash_lookup() function and both mysql and recode have their own hash_insert function.


The IMAP, recode, YAZ and Cyrus extensions cannot be used in conjuction, because they all share the same internal symbol.

Runtime Configuration

This extension has no configuration directives defined in php.ini.

Resource Types

This extension has no resource types defined.

Predefined Constants

This extension has no constants defined.

Table of Contents

recode_file — Recode from file to file according to recode request
recode_string — Recode a string according to a recode request
recode — Alias of recode_string()

Code Examples / Notes » ref.recode


When compiling PHP into Apache as static module Apache configure will complain about an undefined symbol in librecode. You need recode-3.6 (e.g. on to get rid of this error. It doesn't matter if you're compiling PHP as DSO.


I see that the Recode (3.6) module is also incompatible with the MySQL module as well as the others noted in the "warning" note above.


Hope this might help someone:
I tried to compile php 4.3.2-RC2 (+some older versions) with recode AND imap (and gd+png+jpeg support, ldap, gettext, zlib .. but these are not interesting right now).
Why? I needed to run Imp + Horde + Turba. Turba talks to LDAP directory (and LDAP uses utf-8 encoding which I need to convert to iso-8859-2), so I modified Turba to use 'recode' for charset conversions utf8<->iso8859-2.
System: FreeBSD4.7+Apache 1.3.27+Ben SSL
I either could not properly compile OR after compiling apache coredumped.
Problem was: imap (libc-client) and recode (librecode) use the same function hash_lookup(). Therefore during loading (and libraries it depended on) whole apache crashed. Without a word of what's going on.
The problem is detectable by forcing static linking (in FreeBSD modify and change
Now during linking of php the linker complains of double definition of hash_lookup.
-grab recode3.6 from
-unpack, go to src, in files combine.c, hash.c, names.c, recode.c, testdump.c, html.c, hash.h replace hash_lookup() by hash_lookupX() [or invent some better name],
compile recode (i had to do:
setenv CFLAGS "-I/usr/local/include"
setenv LDFLAGS "-L/usr/local/lib -lintl"
./configure --prefix=/usr/local/recode --exec-prefix=/usr/local/recode --without-included-gettext
make check
make install
(recode is installed to /usr/local/recode.You can change this and you can force static linking of recode, so that after building this modified recode is no longer needed and can be deleted! )
For some reason this recode needs to have externally defined
int error;
therefore we have to modify configure script +one .c php source file:
1. modify configure script of php: find
and somewhere before start of main() add
int error;
so the result is:
char *program_name;
int error;
int main() {
; return 0; }
(I modified both occurences of recode_format_table() in configure of php4.3.2rc2)
2. run configure, should work ok (my another problem was with imap: though my c-client was compiled WITHOUT ssl, configure complained that it IS using ssl, so i had to edit configure once again and comment following lines:
void mm_searched(void){}
void mm_expunged(void){}
// char ssl_onceonlyinit();  --- commented
int main() {
// ssl_onceonlyinit(); --- commented
return 0;
Now configure was rather happy :-)
for the record: I did
./configure --with-apxs=/usr/local/apache/bin/apxs --with-imap --enable-sysvsem --enable-sysvshm --with-sybase=/usr/local/freetds --with-gettext --with-ldap --with-zlib --with-recode=/usr/local/recode -with-gd=/usr/local --with-jpeg-dir=/usr/local --with-png-dir=/usr/local
3. edit ext/recode/recode.c (or any other .c source file, add somewhere (e.g. at the end)
int error;
without it during linking 'error not defined' will be complained.
4. do 'make' and php is yours :-)
It took me 2 days.. so do not delete this note, someone might even find it useful and mail me his thanks :-]

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