new file mode 100644
--- /dev/null
+++ b/library/log4php/LoggerFilter.php
@@ -0,0 +1,126 @@
+<?php
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ *       http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * @package log4php
+ */
+
+/**
+ * Users should extend this class to implement customized logging
+ * event filtering. Note that {@link LoggerCategory} and {@link LoggerAppender},
+ * the parent class of all standard
+ * appenders, have built-in filtering rules. It is suggested that you
+ * first use and understand the built-in rules before rushing to write
+ * your own custom filters.
+ *
+ * <p>This abstract class assumes and also imposes that filters be
+ * organized in a linear chain. The {@link #decide
+ * decide(LoggerLoggingEvent)} method of each filter is called sequentially,
+ * in the order of their addition to the chain.
+ *
+ * <p>The {@link decide()} method must return one
+ * of the integer constants {@link LoggerFilter::DENY},
+ * {@link LoggerFilter::NEUTRAL} or {@link LoggerFilter::ACCEPT}.
+ *
+ * <p>If the value {@link LoggerFilter::DENY} is returned, then the log event is
+ * dropped immediately without consulting with the remaining
+ * filters.
+ *
+ * <p>If the value {@link LoggerFilter::NEUTRAL} is returned, then the next filter
+ * in the chain is consulted. If there are no more filters in the
+ * chain, then the log event is logged. Thus, in the presence of no
+ * filters, the default behaviour is to log all logging events.
+ *
+ * <p>If the value {@link LoggerFilter::ACCEPT} is returned, then the log
+ * event is logged without consulting the remaining filters.
+ *
+ * <p>The philosophy of log4php filters is largely inspired from the
+ * Linux ipchains.
+ *
+ * @version $Revision: 1213283 $
+ * @package log4php
+ */
+abstract class LoggerFilter extends LoggerConfigurable {
+
+    /**
+     * The log event must be logged immediately without consulting with
+     * the remaining filters, if any, in the chain.
+     */
+    const ACCEPT = 1;
+
+    /**
+     * This filter is neutral with respect to the log event. The
+     * remaining filters, if any, should be consulted for a final decision.
+     */
+    const NEUTRAL = 0;
+
+    /**
+     * The log event must be dropped immediately without consulting
+     * with the remaining filters, if any, in the chain.
+     */
+    const DENY = -1;
+
+    /**
+     * @var LoggerFilter Points to the next {@link LoggerFilter} in the filter chain.
+     */
+    protected $next;
+
+    /**
+     * Usually filters options become active when set. We provide a
+     * default do-nothing implementation for convenience.
+     */
+    public function activateOptions() {
+    }
+
+    /**
+     * Decide what to do.
+     * <p>If the decision is {@link LoggerFilter::DENY}, then the event will be
+     * dropped. If the decision is {@link LoggerFilter::NEUTRAL}, then the next
+     * filter, if any, will be invoked. If the decision is {@link LoggerFilter::ACCEPT} then
+     * the event will be logged without consulting with other filters in
+     * the chain.
+     *
+     * @param LoggerLoggingEvent $event The {@link LoggerLoggingEvent} to decide upon.
+     * @return integer {@link LoggerFilter::NEUTRAL} or {@link LoggerFilter::DENY}|{@link LoggerFilter::ACCEPT}
+     */
+    public function decide(LoggerLoggingEvent $event) {
+        return self::NEUTRAL;
+    }
+
+    /**
+     * Adds a new filter to the filter chain this filter is a part of.
+     * If this filter has already and follow up filter, the param filter
+     * is passed on until it is the last filter in chain.
+     *
+     * @param $filter - the filter to add to this chain
+     */
+    public function addNext($filter) {
+        if ($this->next !== null) {
+            $this->next->addNext($filter);
+        } else {
+            $this->next = $filter;
+        }
+    }
+
+    /**
+     * Returns the next filter in this chain
+     * @return the next filter
+     */
+    public function getNext() {
+        return $this->next;
+    }
+
+}