diff --git a/extlib/Auth/OpenID/BigMath.php b/extlib/Auth/OpenID/BigMath.php
index 45104947d6..b5fc627a09 100644
--- a/extlib/Auth/OpenID/BigMath.php
+++ b/extlib/Auth/OpenID/BigMath.php
@@ -376,7 +376,7 @@ function Auth_OpenID_detectMathLibrary($exts)
         // Try to load dynamic modules.
         if (!$loaded) {
             foreach ($extension['modules'] as $module) {
-                if (@dl($module . "." . PHP_SHLIB_SUFFIX)) {
+                if (function_exists('dl') && ini_get('enable_dl') && !ini_get('safe_mode') && @dl($module . "." . PHP_SHLIB_SUFFIX)) {
                     $loaded = true;
                     break;
                 }
diff --git a/extlib/Auth/Yadis/XML.php b/extlib/Auth/Yadis/XML.php
index 4854f12bbc..7232d6cbdd 100644
--- a/extlib/Auth/Yadis/XML.php
+++ b/extlib/Auth/Yadis/XML.php
@@ -349,7 +349,7 @@ function &Auth_Yadis_getXMLParser()
     foreach ($extensions as $name => $params) {
         if (!extension_loaded($name)) {
             foreach ($params['libname'] as $libname) {
-                if (@dl($libname)) {
+                if (function_exists('dl') && ini_get('enable_dl') && !ini_get('safe_mode') && @dl($libname)) {
                     $classname = $params['classname'];
                 }
             }
diff --git a/extlib/PEAR.php b/extlib/PEAR.php
index 4c24c6006a..fcefa964a3 100644
--- a/extlib/PEAR.php
+++ b/extlib/PEAR.php
@@ -746,7 +746,7 @@ class PEAR
     {
         if (!extension_loaded($ext)) {
             // if either returns true dl() will produce a FATAL error, stop that
-            if ((ini_get('enable_dl') != 1) || (ini_get('safe_mode') == 1)) {
+            if ((ini_get('enable_dl') != 1) || (ini_get('safe_mode') == 1) || !function_exists('dl')) {
                 return false;
             }
             if (OS_WINDOWS) {
diff --git a/install.php b/install.php
index c49043e5c6..39984aa086 100644
--- a/install.php
+++ b/install.php
@@ -267,12 +267,19 @@ function checkPrereqs()
 
 function checkExtension($name)
 {
-    if (!extension_loaded($name)) {
-        if (!@dl($name.'.so')) {
-            return false;
-        }
+    if (extension_loaded($name)) {
+        return true;
+    } elseif (function_exists('dl') && ini_get('enable_dl') && !ini_get('safe_mode')) {
+    	// dl will throw a fatal error if it's disabled or we're in safe mode.
+    	// More fun, it may not even exist under some SAPIs in 5.3.0 or later...
+    	$soname = $name . '.' . PHP_SHLIB_SUFFIX;
+    	if (PHP_SHLIB_SUFFIX == 'dll') {
+    		$soname = "php_" . $soname;
+    	}
+    	return @dl($soname);
+    } else {
+        return false;
     }
-    return true;
 }
 
 function showLibs()