Installing PHP7 on CentOS 6.8, encountering GLIBC issue

You seem to be trying to install packages from the remi repository (and remi-test for PHP 5.4) but the repository isn't enabled or not present on your system.

If you haven't already installed the remi repository, do that now by installing the appropriate remi-release package.

Then you need to edit /etc/yum.repos.d/remi.repo and change enabled=0 to enabled=1 for the repositories you wish to use. For PHP 5.4 on EL 6, you must enable both remi and remi-test.

You also need to have the EPEL repository installed in order to use remi, though it seems you already have that one.

You've got PHP 5.5 installed from Remi Collet's repo. PHP modules require PHP of same version, because there is binding on binary level.

php-pecl-mongo package from update requires version 5.3, which is available from other/original repos, and you've got 5.5.

try

yum update --enablerepo=remi

If this doesn't work, install required remi-release package: http://blog.famillecollet.com/pages/Config-en

If this doesn't help, then you can either ignore update with --skip-broken or search for mongo module package from other sources.