[-] CORE : file_put_contents() returns the number of bytes that were written to the file, or FALSE on failure.

install-dev/classes/simplexml.php

@@ -65,7 +65,7 @@ class InstallSimplexmlElement extends SimpleXMLElement
 		$dom->loadXML(parent::asXML());
 
 		if ($filename)
-			return file_put_contents($filename, $dom->saveXML());
+			return (bool)file_put_contents($filename, $dom->saveXML());
 		return $dom->saveXML();
 	}
 }