web\basic\config\web.php
........'components' => ['request' => [// !!! insert a secret key in the following (if it is empty) - this is required by cookie validation'cookieValidationKey' => 'zhaoyang',],'mecache' => ['class' => 'yii\caching\MemCache','useMemcached' =>0, //这里简单说明一下 0是memcache, 1是memcached 两个是php里不同的扩展'servers' => [['host' => 'localhost','port' => 11211,]],],'user' => ['identityClass' => 'app\models\User','enableAutoLogin' => true,],
............

　$mecache = Yii::$app->mecache;　$mecache->set("key","value", 60);$mecache->get("key");

web\basic\vendor\yiisoft\yii2\caching\Cache.php
//重写2个方法, 读写都调用这个方法public function myset($key, $value, $duration = 0, $dependency = null)
{return $this->setValue($key, $value, $duration);
}public function myget($key)
{return $this->getValue($key);
}

    public function get($key){$key = $this->buildKey($key);$value = $this->getValue($key);if ($value === false || $this->serializer === false) {return $value;} elseif ($this->serializer === null) {$value = unserialize($value);} else {$value = call_user_func($this->serializer[1], $value);}if (is_array($value) && !($value[1] instanceof Dependency && $value[1]->getHasChanged($this))) {return $value[0];} else {return false;}}public function set($key, $value, $duration = 0, $dependency = null){if ($dependency !== null && $this->serializer !== false) {$dependency->evaluateDependency($this);}if ($this->serializer === null) {$value = serialize([$value, $dependency]);} elseif ($this->serializer !== false) {$value = call_user_func($this->serializer[0], [$value, $dependency]);}$key = $this->buildKey($key);return $this->setValue($key, $value, $duration);}