ElastaticSearch的版本兼容问题以及解决方案

环境：

Ubuntu：

Linux iZ620vnh79jZ 3.13.0-86-generic #130-Ubuntu SMP Mon Apr 18 18:27:15 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux

PHP版本：

PHP 5.5.9-1ubuntu4.21 (cli) (built: Feb  9 2017 20:54:58) 
Copyright (c) 1997-2014 The PHP Group
Zend Engine v2.5.0, Copyright (c) 1998-2014 Zend Technologies
    with XCache v3.1.0, Copyright (c) 2005-2013, by mOo
    with Zend OPcache v7.0.3, Copyright (c) 1999-2014, by Zend Technologies
    with XCache Optimizer v3.1.0, Copyright (c) 2005-2013, by mOo
    with XCache Cacher v3.1.0, Copyright (c) 2005-2013, by mOo
    with XCache Coverager v3.1.0, Copyright (c) 2005-2013, by mOo

Mysql版本：

mysql  Ver 14.14 Distrib 5.5.52, for debian-linux-gnu (x86_64) using readline 6.3

　在搭建ElastaticSearch以后，访问需求端口会出现：

Your version of PHP / json-ext does not support the constant 'JSON_PRESERVE_ZERO_FRACTION',".
            " which is important for proper type mapping in Elasticsearch. Please upgrade your PHP or json-ext.\n".
            "If you are unable to upgrade, and are willing to accept the consequences, you may use the allowBadJSONSerialization()".
            " method on the ClientBuilder to bypass this limitation.

　　这是Elastic的库中出现的问题，对于

JSON_PRESERVE_ZERO_FRACTION
，该常量是在PHP5.6版本之后才引出来的。所以，此处要写兼容的：

解决方案如下：

if(!defined('JSON_PRESERVE_ZERO_FRACTION'))
{
    define('JSON_PRESERVE_ZERO_FRACTION', 1024);
}

　　问题解决！