## exists ##### Description Verify if the specified key exists. 验证一个指定的KEY是否存在 ##### Parameters *key* ##### Return value *BOOL*: If the key exists, return `<span class="calibre12">TRUE</span>`, otherwise return `<span class="calibre12">FALSE</span>`. ##### Examples ``` <pre class="calibre16">$redis->set('key', 'value'); $redis->exists('key'); /* TRUE */ $redis->exists('NonExistingKey'); /* FALSE */ ```