I’m finding that more and more software developers are being quite inconsiderate and are making code that requires PHP 5.3. Since many server-based and long-term support distros are still on PHP 5.2, this can make things difficult quickly.
via Upgrade PHP 5.1/5.2 to 5.3 on CentOS :: Chris Jean.
Here here! I needed to do the following on CentOS 5.7:
#sudo yum erase php
#sudo yum erase php-commons
#sudo yum install php53
#sudo yum install php53-mysql