src/MDC.php

<?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.
 */

namespace Apache\Log4php;

/**
 * The MDC class provides *mapped diagnostic contexts*.
 *
 * A Mapped Diagnostic Context, or MDC in short, is an instrument for
 * distinguishing interleaved log output from different sources. Log output
 * is typically interleaved when a server handles multiple clients
 * near-simultaneously.
 *
 * This class is similar to the {@link NDC} class except that
 * it is based on a map instead of a stack.
 *
 * @license http://www.apache.org/licenses/LICENSE-2.0 Apache License, Version 2.0
 * @link http://logging.apache.org/log4php
 * @since 0.3
 */
class MDC
{
    /** Holds the context map. */
    private static $map = array();

    /**
     * Stores a context value as identified with the key parameter into the
     * context map.
     *
     * @param string $key   the key
     * @param string $value the value
     */
    public static function put($key, $value)
    {
        self::$map[$key] = $value;
    }

    /**
     * Returns the context value identified by the key parameter.
     *
     * @param  string $key The key.
     * @return string The context or an empty string if no context found
     *     for given key.
     */
    public static function get($key)
    {
        return isset(self::$map[$key]) ? self::$map[$key] : '';
    }

    /**
     * Returns the contex map as an array.
     * @return array The MDC context map.
     */
    public static function getMap()
    {
        return self::$map;
    }

    /**
     * Removes the the context identified by the key parameter.
     *
     * Only affects user mappings, not $_ENV or $_SERVER.
     *
     * @param string $key The key to be removed.
     */
    public static function remove($key)
    {
        unset(self::$map[$key]);
    }

    /**
     * Clears the mapped diagnostic context.
     */
    public static function clear()
    {
        self::$map = array();
    }
}