I need help with installation of php-devel (I need it, cause it has phpize, which is necessary to install eAccelerator). But when I try to install php-devel with yum i
Rather than running yum install php-devel you needed to run yum --enablerepo=remi,remi-php54 install php-devel .
In short, just specifying which php-devel version you wanted from the remi repo. In your case you had php54 installed from remi so you needed to add in "remi-php54" . That would have successfully installed php-devel without the downtime.