lsb_release -a
LSB Version:    :base-4.0-amd64:base-4.0-noarch:core-4.0-amd64:core-4.0-noarch:graphics-4.0-amd64:graphics-4.0-noarch:printing-4.0-amd64:printing-4.0-noarch
Distributor ID:    CentOS
Description:    CentOS release 6.9 (Final)
Release:    6.9
Codename:    Final

.检查当前安装的PHP包

yum list installed | grep php
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如果有安装的PHP包，先删除他们

yum remove php.x86_64 php-cli.x86_64 php-common.x86_64 php-gd.x86_64 php-ldap.x86_64 php-mbstring.x86_64 php-mcrypt.x86_64 php-mysql.x86_64 php-pdo.x86_64  
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配置yum源 
CentOS 7.0的源。

yum install epel-release

rpm -ivh http://rpms.famillecollet.com/enterprise/remi-release-7.rpm
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2
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使用yum list命令查看可安装的包(Packege)

yum list --enablerepo=remi --enablerepo=remi-php56 | grep php
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安装PHP5.6.x

yum源配置好了，下一步就安装PHP5.6。

yum install --enablerepo=remi --enablerepo=remi-php56 php php-opcache php-devel php-mbstring php-mcrypt php-mysqlnd php-phpunit-PHPUnit php-pecl-xdebug php-pecl-xhprof
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2用PHP命令查看版本。

php --version

PHP 5.6.0 (cli) (built: Sep  3 2014 19:51:31)

Copyright (c) 1997-2014 The PHP Group

Zend Engine v2.6.0, Copyright (c) 1998-2014 Zend Technologies

    with Zend OPcache v7.0.4-dev, Copyright (c) 1999-2014, by Zend Technologies

    with Xdebug v2.2.5, Copyright (c) 2002-2014, by Derick Rethans
1安装PHP-fpm

yum install --enablerepo=remi --enablerepo=remi-php56 php-fpm 
1在这里安装的版本是PHP5.6.13。

从PHP5.5开始PHP代码缓存从APC变成了Zend OPcache了。

重新启动服务：

在 CentOS 7 系统上:

$ sudo systemctl restart httpd
$ sudo systemctl restart php-fpm
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原文：https://blog.csdn.net/TH_NUM/article/details/78195568