PHP 5.6 on CentOS/RHEL 7.1 and 6.7 via Yum

CentOS/RHEL 7.x

rpm -Uvh https://dl.fedoraproject.org/pub/epel/epel-release-latest-7.noarch.rpm
rpm -Uvh https://mirror.webtatic.com/yum/el7/webtatic-release.rpm

rpm -Uvh https://mirror.webtatic.com/yum/el6/latest.rpm

yum install php56w

If you know what you are doing, you can upgrade PHP by:

yum install yum-plugin-replace
yum replace php-common --replace-with=php56w-common

Package	Provides
php56w	mod_php, php56w-zts
php56w-bcmath
php56w-cli	php-cgi, php-pcntl, php-readline
php56w-common	php-api, php-bz2, php-calendar, php-ctype, php-curl, php-date, php-ereg,,php-exif, php-fileinfo, php-filter, php-ftp, php-gettext, php-gmp,,php-hash, php-iconv, php-json, php-libxml, php-openssl, php-pcre,,php-pecl-Fileinfo, php-pecl-phar, php-pecl-zip, php-reflection,,php-session, php-shmop, php-simplexml, php-sockets, php-spl,,php-tokenizer, php-zend-abi, php-zip, php-zlib
php56w-dba
php56w-devel
php56w-embedded	php-embedded-devel
php56w-enchant
php56w-fpm
php56w-gd
php56w-imap
php56w-interbase	php_database, php-firebird
php56w-intl
php56w-ldap
php56w-mbstring
php56w-mcrypt
php56w-mssql
php56w-mysql	php-mysqli, php_database
php56w-mysqlnd	php-mysqli, php_database
php56w-odbc	php-pdo_odbc, php_database
php56w-opcache	php56w-pecl-zendopcache
php56w-pdo
php56w-pear
php56w-pecl-apcu
php56w-pecl-gearman
php56w-pecl-geoip
php56w-pecl-imagick
php56w-pecl-memcache
php56w-pecl-xdebug
php56w-pgsql	php-pdo_pgsql, php_database
php56w-phpdbg
php56w-process	php-posix, php-sysvmsg, php-sysvsem, php-sysvshm
php56w-pspell
php56w-recode
php56w-snmp
php56w-soap
php56w-tidy
php56w-xml	php-dom, php-domxml, php-wddx, php-xsl
php56w-xmlrpc

yum install php56w-opcache