dl

(PHP 4, PHP 5)

dl — Carica i moduli del PHP a runtime

Descrizione

int dl ( string $library )

La funzione carica il modulo di PHP passato nel parametro library. Il parametro library indica soltanto il nome del file del modulo da caricare il quale può dipendere dal piattaforma utilizzata. Ad esempio il modulo sockets (se compilato come modulo condiviso, non è il default!) sulle piattaforme Unix si chiama sockets.so, mentre in Windows si chiama php_sockets.dll.

Restituisce TRUE in caso di successo, FALSE in caso di fallimento. Se la funzionalità di carico dei moduli non è disponibile (vedi note), oppure è stata disabilitata (sia disabilitando enable_dl oppure attivando modalità sicura nel php.ini), sarà generato un E_ERROR e sarà bloccata l'esecuzione dello script. Se dl() fallisce perché non riesce a caricare la libreria indicata, oltre a restituire FALSE verrà generato un messaggio di tipo E_WARNING.

Si può utilizzare extension_loaded() per testare se un modulo è veramente affidabile o meno. Questa funzione si applica sia a moduli built-in sia ai moduli caricati (tramite php.ini oppure dl()).

La funzione dl() è deprecata dal PHP 5. Piuttosto utilizzare Parametri per il carico dei moduli.

Example #1 Esempio di uso di dl()


<?php
// Caricare un modulo in base al sistema operativo
if (!extension_loaded('sqlite')) {
    if (strtoupper(substr(PHP_OS, 0, 3) == 'WIN')) {
        dl('php_sqlite.dll');
    } else {
        dl('sqlite.so');
    }
}

// Oppure la costante PHP_SHLIB_SUFFIX disponibile da 4.3.0
if (!extension_loaded('sqlite')) {
    $prefix = (PHP_SHLIB_SUFFIX == 'dll') ? 'php_' : '';
    dl($prefix . 'sqlite.' . PHP_SHLIB_SUFFIX);
}
?>

La directory da cui vengono caricate le estensioni dipende dal sistema operativo della macchina:

Windows - Se non viene impostato esplicitamente nel php.ini, i moduli sono caricati da c:\php4\extensions\ .

Unix - Se non viene impostato esplicitamente nel php.ini, la directory di default dipenda da

se il PHP è stato compilato con --enable-debug o meno
se il PHP è stato compilato con (versione sperimentale) ZTS (Zend Thread Safety) o meno
il valore attuale di ZEND_MODULE_API_NO (numero interno del modulo API Zend, il quale indica la data in cui si sono apportate le maggiori modifiche al modulo, ad esempio 20010901)

Quindi considerando quanto detto, la directory di default può essere <install-dir>/lib/php/extensions/ <debug-or-not>-<zts-or-not>-ZEND_MODULE_API_NO, /usr/local/php/lib/php/extensions/debug-non-zts-20010901 oppure /usr/local/php/lib/php/extensions/no-debug-zts-20010901.

Nota:
La funzione dl() non è supportata dai web server multithread. Utilizzare il parametro del php.ini extensions quando si debba utilizzare tali server. Mentre le versioni CGI e CLI non hanno questa limitazione.

Nota:
La dl() è sensibile alla maiuscole sulle piattaforme Unix.

Nota: Questa funzione è disabilitata nella modalitàsafe-mode

Vedere anche Direttive per il carimaneto dei moduli e extension_loaded().

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User Contributed Notes 6 notes

down

shaunspiller at spammenot-gmail dot com ¶

6 years ago


dl is awkward because the filename format is OS-dependent and because it can complain if the extension is already loaded. This wrapper function fixes that:

<?php

function load_lib($n, $f = null) {
    return extension_loaded($n) or dl(((PHP_SHLIB_SUFFIX === 'dll') ? 'php_' : '') . ($f ? $f : $n) . '.' . PHP_SHLIB_SUFFIX);
}

?>

Examples:

<?php

// ensure we have SSL and MySQL support
load_lib('openssl');
load_lib('mysql');

// a rare few extensions have a different filename to their extension name, such as the image (gd) library, so we specify them like this:
load_lib('gd', 'gd2');

?>

down

endofyourself at yahoo dot com ¶

11 years ago


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()



?>

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-1

K. C. ¶

2 months ago


It would be nice to know which SAPIs removed the function. 

Telling me 'This function has been removed from some SAPIs in PHP 5.3.' is pretty much useless and I feel mocked. Or do the writers of the documentation don't know from which SAPIs it has been removed?

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-1

mag_2000 at front dot ru ¶

9 years ago


<?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()

?>

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-1

Anonymous ¶

4 years ago


this function errors out as the dl() cannot take the absolute path..."Warning: dl() [function.dl]: Temporary module name should contain only filename in /home/..."

down

-4

fabrizim at owlwatch dot com ¶

1 year ago


As noted in the documentation:

Changelog 5.3: dl() is now disabled in some SAPIs due to stability issues. The only SAPIs that allow dl() are CLI and Embed. Use the Extension Loading Directives instead.

If using PEAR libraries that try to load extensions, like Image_Transform which will try to load ImageMagik, and the "enable_dl" directive is set to 1 in your php.ini, you may end up with a hard to find error (white screen of death).

One "solution" is to change the enable_dl directive to 0 in the php.ini. It may have adverse affects if you are using php on command line that requires the "dl" function, but I think in most cases its okay.

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