RPM of PHP 5.3.12 are available for Enterprise Linux in remi repository.
RPM of PHP 5.4.2 are available for Fedora in remi repository and for Enterprise Linux in remi-test repository.
Read the announcement : PHP 5.3.12 and PHP 5.4.2 Released!
Use YUM to install : yum --enablerepo=remi update php-\* For all questions or help, please use the Forums.... Lire php-5.3.12 and php-5.4.2