diff --git a/adminer/drivers/mysql.inc.php b/adminer/drivers/mysql.inc.php
index 55d31df8..11c3314f 100644
--- a/adminer/drivers/mysql.inc.php
+++ b/adminer/drivers/mysql.inc.php
@@ -202,7 +202,7 @@ if (!defined("DRIVER")) {
 			/** Free result set
 			*/
 			function __destruct() {
-				mysql_free_result($this->_result); //! not called in PHP 4 which is a problem with mysql.trace_mode
+				mysql_free_result($this->_result);
 			}
 		}
 
diff --git a/compile.php b/compile.php
index cf64a20c..3d6b683b 100755
--- a/compile.php
+++ b/compile.php
@@ -394,5 +394,5 @@ $file = preg_replace("~<\\?php\\s*\\?>\n?|\\?>\n?<\\?php~", '', $file);
 $file = php_shrink($file);
 
 $filename = $project . (preg_match('~-dev$~', $VERSION) ? "" : "-$VERSION") . ($driver ? "-$driver" : "") . ($_SESSION["lang"] ? "-$_SESSION[lang]" : "") . ".php";
-fwrite(fopen($filename, "w"), $file); // file_put_contents() since PHP 5
+file_put_contents($filename, $file);
 echo "$filename created (" . strlen($file) . " B).\n";
diff --git a/editor/include/editing.inc.php b/editor/include/editing.inc.php
index 62867047..32d3f4ef 100644
--- a/editor/include/editing.inc.php
+++ b/editor/include/editing.inc.php
@@ -4,7 +4,7 @@
 * @return string
 */
 function email_header($header) {
-	// iconv_mime_encode requires PHP 5, imap_8bit requires IMAP extension
+	// iconv_mime_encode requires iconv, imap_8bit requires IMAP extension
 	return "=?UTF-8?B?" . base64_encode($header) . "?="; //! split long lines
 }
 
diff --git a/lang.php b/lang.php
index c289e546..28ce433d 100755
--- a/lang.php
+++ b/lang.php
@@ -56,7 +56,7 @@ foreach (glob(dirname(__FILE__) . "/adminer/lang/" . ($_SESSION["lang"] ? $_SESS
 	}
 	$s = "<?php\n\$translations = array(\n$s);\n";
 	if ($s != $file) {
-		fwrite(fopen($filename, "w"), $s); // file_put_contents() since PHP 5
+		file_put_contents($filename, $s);
 		echo "$filename updated.\n";
 	}
 }
diff --git a/plugins/plugin.php b/plugins/plugin.php
index 8762330d..0137b6b3 100644
--- a/plugins/plugin.php
+++ b/plugins/plugin.php
@@ -24,26 +24,17 @@ class AdminerPlugin extends Adminer {
 		if ($plugins === null) {
 			$plugins = array();
 			foreach (get_declared_classes() as $class) {
-				if (preg_match('~^Adminer.~i', $class) && strcasecmp($this->_findRootClass($class), 'Adminer')) { // can use interface since PHP 5
+				if (preg_match('~^Adminer.~i', $class) && strcasecmp($this->_findRootClass($class), 'Adminer')) { //! can use interface
 					$plugins[$class] = new $class;
 				}
 			}
 		}
 		$this->plugins = $plugins;
-		// it is possible to use ReflectionObject in PHP 5 to find out which plugins defines which methods at once
+		//! it is possible to use ReflectionObject to find out which plugins defines which methods at once
 	}
 	
 	function _callParent($function, $args) {
-		switch (count($args)) { // call_user_func_array(array('parent', $function), $args) works since PHP 5
-			case 0: return parent::$function();
-			case 1: return parent::$function($args[0]);
-			case 2: return parent::$function($args[0], $args[1]);
-			case 3: return parent::$function($args[0], $args[1], $args[2]);
-			case 4: return parent::$function($args[0], $args[1], $args[2], $args[3]);
-			case 5: return parent::$function($args[0], $args[1], $args[2], $args[3], $args[4]);
-			case 6: return parent::$function($args[0], $args[1], $args[2], $args[3], $args[4], $args[5]);
-			default: trigger_error('Too many parameters.', E_USER_WARNING);
-		}
+		return call_user_func_array(array('parent', $function), $args);
 	}
 	
 	function _applyPlugin($function, $args) {