PHP 选项/信息 函数
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dl

(PHP 4, PHP 5)

dl — Loads a PHP extension at runtime

说明

bool dl ( string $library )

Loads the PHP extension given by the parameter library.

Use extension_loaded() to test whether a given extension is already available or not. This works on both built-in extensions and dynamically loaded ones (either through php.ini or dl()).

Warning

This function has been removed from some SAPIs in PHP 5.3.

参数

library

This parameter is only the filename of the extension to load which also depends on your platform. For example, the sockets extension (if compiled as a shared module, not the default!) would be called sockets.so on Unix platforms whereas it is called php_sockets.dll on the Windows platform.

The directory where the extension is loaded from depends on your platform:

Windows - If not explicitly set in the php.ini, the extension is loaded from C:\php4\extensions\ (PHP 4) or C:\php5\ (PHP 5) by default.

Unix - If not explicitly set in the php.ini, the default extension directory depends on

  • whether PHP has been built with --enable-debug or not
  • whether PHP has been built with (experimental) ZTS (Zend Thread Safety) support or not
  • the current internal ZEND_MODULE_API_NO (Zend internal module API number, which is basically the date on which a major module API change happened, e.g. 20010901)
Taking into account the above, the directory then defaults to <install-dir>/lib/php/extensions/ <debug-or-not>-<zts-or-not>-ZEND_MODULE_API_NO, e.g. /usr/local/php/lib/php/extensions/debug-non-zts-20010901 or /usr/local/php/lib/php/extensions/no-debug-zts-20010901.

返回值

成功时返回 TRUE， 或者在失败时返回 FALSE. If the functionality of loading modules is not available or has been disabled (either by setting enable_dl off or by enabling 安全模式 in php.ini) an E_ERROR is emitted and execution is stopped. If dl() fails because the specified library couldn't be loaded, in addition to FALSE an E_WARNING message is emitted.

范例

Example #1 dl() examples

<?php
// Example loading an extension based on OS
if (!extension_loaded('sqlite')) {
    if (strtoupper(substr(PHP_OS, 0, 3)) === 'WIN') {
        dl('php_sqlite.dll');
    } else {
        dl('sqlite.so');
    }
}

// Or, the PHP_SHLIB_SUFFIX constant is available as of PHP 4.3.0
if (!extension_loaded('sqlite')) {
    $prefix = (PHP_SHLIB_SUFFIX === 'dll') ? 'php_' : '';
    dl($prefix . 'sqlite.' . PHP_SHLIB_SUFFIX);
}
?>

更新日志

版本 说明
5.3.0 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.

注释

Note:

dl() is not supported when PHP is built with ZTS support. Use the Extension Loading Directives instead.

Note:

dl() is case sensitive on Unix platforms.

Note: 当 PHP 运行在 安全模式 时，不能使用此函数。

参见

PHP 选项/信息 函数
在线手册：中文 英文
PHP手册
PHP手册 - N: Loads a PHP extension at runtime

用户评论:

Anonymous (04-Dec-2010 06:36)

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/..."

CLI workaround (18-Feb-2009 11:18)

NOTE:  This only works using the CLI

If you need to use dl() with the CLI, but you get this warning:

"PHP Warning:  dl(): Dynamically loaded extensions aren't enabled"

Then the 'enable_dl' setting in the php.ini needs to be set to 'On' - the set_ini() function does not work with this INI option.

If, however, you do not wish (or don't have access) to alter the system php.ini, then you can do the following:

<?php

if ( !ini_get('enable_dl') ) {
    exec("php -d enable_dl=On $argv[0]");
    exit;
}

?>

This simply calls itself and defines the enable_dl INI entry on the command line so you dont have to start the script with options in the first place (or use another script to call it.)

shaunspiller at spammenot-gmail dot com (29-Jan-2009 08:34)

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');

?>

buildsmart at daleenterprise dot com (29-Dec-2006 09:33)

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

docey (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)

<?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 (19-Jul-2005 12:30)

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 12:12)

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 04:15)

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