>PHP: dl - Manual

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int dl ( string biblioteca )

Carga la extensiÃ³n PHP dada por el parÃ¡metro biblioteca. El parÃ¡metro biblioteca es Ãºnicamente el nombre de archivo de la extensiÃ³n a cargar, el cual tambiÃ©n depende de su plataforma. Por ejemplo, la extensiÃ³n sockets (si fue compilada como mÃ³dulo, Â¡que no es el comportamiento predeterminado!) podrÃa llamarse sockets.so en plataformas Unix, mientras que se llama php_sockets.dll en la plataforma windows.

Devuelve TRUE si todo se llevÃ³ a cabo correctamente, FALSE en caso de fallo. Si la funcionalidad de carga de mÃ³dulos no estÃ¡ disponible (ver Nota) o ha sido deshabilitada (ya sea mediante la desactivaciÃ³n de enable_dl o activando safe mode en php.ini) un E_ERROR es producido y se detiene la ejecuciÃ³n. Si dl() falla porque la biblioteca especificada no pudo ser cargada, se emite un mensaje E_WARNING en compaÃ±Ãa del FALSE.

Use extension_loaded() para probar si una cierta extensiÃ³n ya se encuentra disponible o no. Esto funciona tanto con extensiones integradas como con las cargadas dinÃ¡micamente (ya sea mediante php.ini o dl()).

La funciÃ³n dl() es obsoleta a partir de PHP 5. Use el mÃ©todo de las Directivas de Carga de Extensiones en su lugar.

Ejemplo 1. Ejemplos de dl()


<?php

// Ejemplo de carga de una extension 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 esta disponible a

// partir de PHP 4.3.0

if (!extension_loaded('sqlite')) {

    $prefijo = (PHP_SHLIB_SUFFIX === 'dll') ? 'php_' : '';

    dl($prefijo . 'sqlite.' . PHP_SHLIB_SUFFIX);

}

?>

El directorio desde donde es cargada la extensiÃ³n depende de su plataforma:

Windows - Si no estÃ¡ definida explÃcitamente en php.ini, la extensiÃ³n es cargada desde c:\php4\extensions\ por defecto.

Unix - Si no estÃ¡ definida explÃcitamente 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 (nÃºmero interno de API de mÃ³dulo Zend, el cual es bÃ¡sicamente la fecha en la que ocurriÃ© un cambio significativo en la API de mÃ³dulo, p.ej. 20010901)

Tomando en cuenta lo anterior, el directorio recibe el valor predeterminado de <dir-instalacion>/lib/php/extensions/ <debug-o-no>-<zts-o-no>-ZEND_MODULE_API_NO, p.ej. /usr/local/php/lib/php/extensions/debug-non-zts-20010901 o /usr/local/php/lib/php/extensions/no-debug-zts-20010901.

Nota: La funciÃ³n 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, Â¡las versiones CGI y CLI no son afectadas!

Nota: dl() es sensible a mayÃºsculas y minÃºsculas en plataformas Unix.

Nota: Esta funciÃ³n no estÃ¡ habilitada en safe-mode (modo-seguro)

Vea tambiÃ©n Directivas de Carga de ExtensiÃ³n y extension_loaded().

add a note User Contributed Notes
dl

docey
30-Dec-2005 09:37


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,



// 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 11:13


<?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 04:30


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

nutbar at innocent dot com
18-Mar-2004 01:22


For those who are tearing their hair out due to the extension_dir being set to "./", here's a somewhat graceful fix that will be portable:



dl(preg_replace('/\/([^\/]+)/', '../', dirname(__FILE__)) . __FILE__ . '/../some/path/dll.so');



You could alternatively make that preg_replace part into a separate function and call it something like dirname_rel() or whatever.  It basically replaces all the path components with ".." and spits out a relative path, so that when mixed with the "./" part of the extension_dir setting, it puts you at the root folder "/" so that you know where you are :)

endofyourself at yahoo dot com
18-Oct-2003 04:12


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



---------------

/*

    Function: dl_local()

    Reference: http://us2.php.net/manual/en/http://indices.com.es/function.dl.html

    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/http://indices.com.es/function.get-extension-funcs.html".

*/



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
05-Jul-2003 08:15


Alan isn't 100% correct (though he's close). The exception is Mac OS X. This operating system makes a distinction between dynamically loadable shared libraries and 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

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