assert
I recently came across this under PHP 4.4.4, it seems that the dl(); function generates an error/warning about registering the function if a test is done on an extension that is pre-loaded in the php.ini file (extension=gd.so).
<?php
$gd_is_shared = "shared-library";
if (function_exists('ImageCreateFromPNG') && !@dl('gd.so')) {
$gd_is_shared = "embedded";
}
print $gd_is_shared;
?>
The only purpose of this test is to determine if it is an embedded extension or a loaded extension.
I don't see this error occur under PHP 5.1.6 or PHP 5.2.0.
The test platform is Mac OS X 10.3.9 and Mac OS X 10.4.8
dl
(PHP 4, PHP 5)
dl — Carga una extensión PHP en tiempo de ejecución
Descripción
int dl
( string $biblioteca
)
Carga la extensión PHP dada por el parámetro biblioteca .
Use extension_loaded() para probar si una cierta extensión ya se encuentra disponible o no. Esto funciona tanto con extensiones integradas como con las cargadas dinámicamente (ya sea mediante php.ini o dl()).
Lista de parámetros
- biblioteca
-
Este parámetro es únicamente el nombre de archivo de la extensión a cargar, el cual también depende de su plataforma. Por ejemplo, la extensión sockets (si fue compilada como módulo, ¡que no es el comportamiento predeterminado!) podría llamarse sockets.so en plataformas Unix, mientras que se llama php_sockets.dll en la plataforma Windows.
El directorio desde donde es cargada la extensión depende de su plataforma:
Windows - Si no está definida explícitamente en php.ini, la extensión es cargada desde c:\php4\extensions\ por defecto.
Unix - Si no está definida explícitamente en php.ini, el directorio de extensiones predeterminado depende de
- si PHP ha sido compilado con --enable-debug o no
- si PHP ha sido compilado con soporte ZTS (Zend Thread Safety) (experimental) o no
- el valor interno ZEND_MODULE_API_NO actual (número interno de API de módulo Zend, el cual es básicamente la fecha en la que ocurrió un cambio significativo en la API de módulo, p.ej. 20010901)
Valores retornados
Devuelve TRUE si todo se llevó a cabo correctamente, FALSE en caso de fallo. Si la funcionalidad de carga de módulos no está disponible (ver Nota) o ha sido deshabilitada (ya sea mediante la desactivación de enable_dl o activando safe mode en php.ini) un E_ERROR es producido y se detiene la ejecución. Si dl() falla porque la biblioteca especificada no pudo ser cargada, se emite un mensaje E_WARNING en compañía del FALSE.
Ejemplos
Example #1 Ejemplos de dl()
<?php
// Ejemplo de carga de una extensión en base al SO
if (!extension_loaded('sqlite')) {
if (strtoupper(substr(PHP_OS, 0, 3)) === 'WIN') {
dl('php_sqlite.dll');
} else {
dl('sqlite.so');
}
}
// O, usando la constante PHP_SHLIB_SUFFIX que está disponible a
// partir de PHP 4.3.0
if (!extension_loaded('sqlite')) {
$prefijo = (PHP_SHLIB_SUFFIX === 'dll') ? 'php_' : '';
dl($prefijo . 'sqlite.' . PHP_SHLIB_SUFFIX);
}
?>
Notes
Note: La función dl() no es soportada en servidores Web multi-hilos. Use la sentencia extensions en su php.ini cuando trabaje sobre ese tipo de entornos. Sin embargo, ¡las versiones CGI y CLI no son afectadas!
Note: A partir de PHP 5, la función dl() es considerada obsoleta en todas las SAPI excepto CLI. Use el método de las Directivas de Carga de Extensiones en su lugar.
Note: A partir de PHP 6 esta función es desahibilatad en todas las SAPIs, excepto CLI, CGI y embed.
Note: dl() es sensible a mayúsculas y minúsculas en plataformas Unix.
Note: Esta función no está habilitada en safe-mode (modo-seguro)
add a note
User Contributed Notesdl
buildsmart at daleenterprise dot com
29-Dec-2006 09:33
29-Dec-2006 09:33
prozente
23-Nov-2006 11:57
23-Nov-2006 11:57
a note for mag_2000 at front dot ru
the line
$currentExtPath = ini_get('extension_dir');
would be better to be
$currentExtPath = realpath(ini_get('extension_dir'));
I came across some hosts that had ./ set at the extension_dir
docey
31-Dec-2005 05:37
31-Dec-2005 05:37
just some note to loading modules, they do not have to
be executable.
some examples below check for this but if an module is
not executable is does not mean you cant use it. it just
needs to be readable NOT executable.
although some modules might need this perhaps for some
reason i cannot think of, so here an example,
<?php
// fails to load mysql although it could be loaded.
if(is_executable("mysql.so")){
dl("mysql.so");
}
// loads mysql
if(is_readable("mysql.so")){
dl("mysql.so");
}
?>
watch out with this, as you can see mysql.so would not be
loaded and the script would fail. because its checked for
executable permissions although these are not needed.
mag_2000 at front dot ru
06-Dec-2005 07:13
06-Dec-2005 07:13
<?php
function dl_local( $extensionFile ) {
//make sure that we are ABLE to load libraries
if( !(bool)ini_get( "enable_dl" ) || (bool)ini_get( "safe_mode" ) ) {
die( "dh_local(): Loading extensions is not permitted.\n" );
}
//check to make sure the file exists
if( !file_exists( $extensionFile ) ) {
die( "dl_local(): File '$extensionFile' does not exist.\n" );
}
//check the file permissions
if( !is_executable( $extensionFile ) ) {
die( "dl_local(): File '$extensionFile' is not executable.\n" );
}
//we figure out the path
$currentDir = getcwd() . "/";
$currentExtPath = ini_get( "extension_dir" );
$subDirs = preg_match_all( "/\//" , $currentExtPath , $matches );
unset( $matches );
//lets make sure we extracted a valid extension path
if( !(bool)$subDirs ) {
die( "dl_local(): Could not determine a valid extension path [extension_dir].\n" );
}
$extPathLastChar = strlen( $currentExtPath ) - 1;
if( $extPathLastChar == strrpos( $currentExtPath , "/" ) ) {
$subDirs--;
}
$backDirStr = "";
for( $i = 1; $i <= $subDirs; $i++ ) {
$backDirStr .= "..";
if( $i != $subDirs ) {
$backDirStr .= "/";
}
}
//construct the final path to load
$finalExtPath = $backDirStr . $currentDir . $extensionFile;
//now we execute dl() to actually load the module
if( !dl( $finalExtPath ) ) {
die();
}
//if the module was loaded correctly, we must bow grab the module name
$loadedExtensions = get_loaded_extensions();
$thisExtName = $loadedExtensions[ sizeof( $loadedExtensions ) - 1 ];
//lastly, we return the extension name
return $thisExtName;
}//end dl_local()
?>
james at gogo dot co dot nz
18-Jul-2005 11:30
18-Jul-2005 11:30
WARNING: enable_dl/dl()
*********************
There is an exploit circulating currently which takes advantage of dl() to inject code into Apache which causes all requests to all virtual hosts to be redirected to a page of the attackers choice.
All operators of shared web hosting servers with Apache and PHP should disable dl() by setting enable_dl to off otherwise your servers are vulnerable to this exploit.
This exploit is generally known as flame.so (the object that is loaded into Apache) and flame.php (the php script that loads it).
Google gives more information:
http://www.google.co.nz/search?q=flame.so+flame.php
endofyourself at yahoo dot com
18-Oct-2003 11:12
18-Oct-2003 11:12
If you need to load an extension from the CURRENT local directory because you do not have privelages to place the extension in your servers PHP extensions directory, this function i wrote may be of use to you
<?php
/*
Function: dl_local()
Reference: http://us2.php.net/manual/en/function.dl.php
Author: Brendon Crawford <endofyourself |AT| yahoo>
Usage: dl_local( "mylib.so" );
Returns: Extension Name (NOT the extension filename however)
NOTE:
This function can be used when you need to load a PHP extension (module,shared object,etc..),
but you do not have sufficient privelages to place the extension in the proper directory where it can be loaded. This function
will load the extension from the CURRENT WORKING DIRECTORY only.
If you need to see which functions are available within a certain extension,
use "get_extension_funcs()". Documentation for this can be found at
"http://us2.php.net/manual/en/function.get-extension-funcs.php".
*/
function dl_local( $extensionFile ) {
//make sure that we are ABLE to load libraries
if( !(bool)ini_get( "enable_dl" ) || (bool)ini_get( "safe_mode" ) ) {
die( "dh_local(): Loading extensions is not permitted.\n" );
}
//check to make sure the file exists
if( !file_exists( $extensionFile ) ) {
die( "dl_local(): File '$extensionFile' does not exist.\n" );
}
//check the file permissions
if( !is_executable( $extensionFile ) ) {
die( "dl_local(): File '$extensionFile' is not executable.\n" );
}
//we figure out the path
$currentDir = getcwd() . "/";
$currentExtPath = ini_get( "extension_dir" );
$subDirs = preg_match_all( "/\//" , $currentExtPath , $matches );
unset( $matches );
//lets make sure we extracted a valid extension path
if( !(bool)$subDirs ) {
die( "dl_local(): Could not determine a valid extension path [extension_dir].\n" );
}
$extPathLastChar = strlen( $currentExtPath ) - 1;
if( $extPathLastChar == strrpos( $currentExtPath , "/" ) ) {
$subDirs--;
}
$backDirStr = "";
for( $i = 1; $i <= $subDirs; $i++ ) {
$backDirStr .= "..";
if( $i != $subDirs ) {
$backDirStr .= "/";
}
}
//construct the final path to load
$finalExtPath = $backDirStr . $currentDir . $extensionFile;
//now we execute dl() to actually load the module
if( !dl( $finalExtPath ) ) {
die();
}
//if the module was loaded correctly, we must bow grab the module name
$loadedExtensions = get_loaded_extensions();
$thisExtName = $loadedExtensions[ sizeof( $loadedExtensions ) - 1 ];
//lastly, we return the extension name
return $thisExtName;
}//end dl_local()
?>
tychay at php dot net
06-Jul-2003 03:15
06-Jul-2003 03:15
MacOS makes a distinction between dynamically loadable shared libraries and loadable modules of code (bundles). The former has an extension .dylib and the latter has an extension .so. The former is in Mac-O and the latter is in ELF.
Thus PHP's extensions are built as .so whereas the symbol PHP_SHLIB_SUFFIX is bound (currently) to .dylib. I don't think this is the correct behavior, but nonetheless, it is the behavior as of PHP-5.0.0b2-dev. Right now, the config binds to SHLIB_SUFFIX_NAME (which is correctly bound to .dylib on Mac OS X). I imagine this is related to why there is so much trouble getting dl() to work on Mac OS X. (For instance, I have no trouble phpizing in a new shared library, but when compiling in stuff as shared... much evilness!)
BTW, to get dl() to work in Mac OS X you need to install the dlcompat library (via Fink, DarwinPorts, or Gentoo ports). Remember in the case of Fink, you better make sure your environment variables are adjusted to point to where dlcompat (and your other fink libraries) are.
terry