Firstly, you may need to import/installl remi repos and development tools into your CentOS.
Then, install php,apache and freetds using yum :
#yum install httpd php freetds freetds-devel
#php -i (to identify php version installed)
Go to php.net and download the php souce code same version as above.
Extract it, and be prepare to compile the souce code.
# cp modules/sybase_ct.so /usr/lib64/php/modules
and enter the following text;
; Enable SAIBESSSS extension module
restart your apache, and create file contain <?php phpinfo(); ?> to check whether the module successfully installed or not. You also can check from terminal by running # php -i | grep sybase
Teston On CentOS 6.6 , PHP 5.4.38, Apache 2.2