Missing the php-mysql mod for PHP I'll bet. What does: php -m |grep mysql show?
If it shows nothing missing the php-mysql and php-mysqli modules.
How to acquire them depends upon what repo one is using and how yum is set up:
yum repolist
shows what repos your server is set to check
yum list php-m*
Will show all php exetensions that have -m in their name.
You need to acquire the php-mysql and php-mysqli from the same repo you acquired the PHP you've installed.
For example ... I use webtatic repo for PHP ... the names of their packages are slightly different than those found with default CentOS packages thus have to issue yum using the following:
yum list php55w-m*
which shows something like the following on a brand new CentOS 6.6 boxen:
* webtatic: us-east.repo.webtatic.com
Installed Packages
php55w-mbstring.x86_64 5.5.18-1.w6 @webtatic
php55w-mcrypt.x86_64 5.5.18-1.w6 @webtatic
php55w-mssql.x86_64 5.5.18-1.w6 @webtatic
php55w-mysql.x86_64 5.5.18-1.w6 @webtatic
Available Packages
php55w-mysqlnd.x86_64 5.5.18-1.w6 webtatic
Once you install the required php-mysql extension restart apache.
BTW, with CentOS, one gets php-mysqli also when one installs php-mysql - you need the php-mysqli (see the 'i' at the end?)
/sbin/service httpd restart
Then attempt to install again.
'spirit of sharing', Ken