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
説明
int dl ( string library )library で指定された PHP 拡張モジュールを ロードします。 library に指定できるのは拡張モジュールの ファイル名だけであり、それはプラットフォームに 依存します。例えば、Unix プラットフォームでは sockets 拡張モジュール (共有モジュールとしてコンパイルされていれば。デフォルトでは有りません!) は sockets.so と呼ばれていますし、一方 Windows プラットフォームでは php_sockets.dll と呼ばれます。
成功した場合に TRUE を、失敗した場合に FALSE を返します。 拡張モジュールのロード機能が無効(注意書き参照)だったり、あるいは 無効化されている(enable_dl でオフにされているか または php.ini で セーフモード が有効になっている)場合は、 E_ERROR を発行して実行は停止されます。 指定されたライブラリをロードできず dl() が 失敗した場合、FALSE に加えて E_WARNING メッセージが 発行されます。
extension_loaded() で、指定された拡張モジュールが 既に有効かどうか調べることができます。ビルトインの拡張モジュールと 動的なものと両方を調べることができます(php.ini で指定されたものも dl() でロードされたものも)。
PHP 5 では、CLI 以外の あらゆる SAPI において dl() 関数が非推奨となっています。 代わりに、拡張モジュール 読み込み用のディレクティブを利用してください。
拡張モジュールがロードされるディレクトリはプラットフォームによって 違います:
Windows - php.ini に明記されていない場合、デフォルトでは 拡張モジュールは c:\php4\extensions\ から ロードされます。
Unix - php.ini に明記されていない場合、デフォルトでは 以下に依存します。
PHP をビルドする際に --enable-debug を指定しているか否か
PHP をビルドする際に(実験段階の)ZTS (Zend Thread Safety)サポートを 有効にしているか否か
現在の ZEND_MODULE_API_NO(Zend 内部モジュール API 番号。基本的にはメジャーモジュール API の変更が発生した日時。 例:20010901)
注意: dl() はマルチスレッド Web サーバ上では サポートされません。 そのような環境の場合には php.ini 上で extensions 命令を使用するようにしてください。しかし、CGI や CLI には 影響しません!
注意: PHP 6 以降では、CLI, CGI および埋め込み版 (embed) を除くすべての SAPI でこの関数は無効となっています。
注意: dl() は Unix プラットフォーム上では 大文字小文字を区別します。
注意: この関数は、safe-mode では無効となります。
Extension Loading Directives extension_loaded() も参照してください。
dl
buildsmart at daleenterprise dot com
30-Dec-2006 06:33
30-Dec-2006 06:33
prozente
23-Nov-2006 08:57
23-Nov-2006 08:57
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 02:37
31-Dec-2005 02:37
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
07-Dec-2005 04:13
07-Dec-2005 04:13
<?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 08:30
19-Jul-2005 08:30
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
19-Mar-2004 06:22
19-Mar-2004 06:22
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 08:12
18-Oct-2003 08:12
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/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 12:15
06-Jul-2003 12:15
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