Here is what 'yum install php-7.2.3' returns:
[root@prv-apps conf.d]# yum install php-7.2.3
Loaded plugins: fastestmirror, langpacks
Loading mirror speeds from cached hostfile
* base: mirror.vtti.vt.edu
* epel: ftp.cse.buffalo.edu
* extras: mirror.vtti.vt.edu
* remi-php72: mirror.team-cymru.org
* remi-safe: mirror.team-cymru.org
* updates: mirror.vtti.vt.edu
Resolving Dependencies
--> Running transaction check
---> Package php.x86_64 0:5.4.16-43.el7_4.1 will be updated
---> Package php.x86_64 0:7.2.3-2.el7.remi will be an update
--> Processing Dependency: php-common(x86-64) = 7.2.3-2.el7.remi for package: php-7.2.3-2.el7.remi.x86_64
--> Processing Dependency: php-cli(x86-64) = 7.2.3-2.el7.remi for package: php-7.2.3-2.el7.remi.x86_64
--> Processing Dependency: libargon2.so.0()(64bit) for package: php-7.2.3-2.el7.remi.x86_64
--> Running transaction check
---> Package libargon2.x86_64 0:20161029-2.el7 will be installed
---> Package php-cli.x86_64 0:5.4.16-43.el7_4.1 will be updated
--> Processing Dependency: php-cli(x86-64) = 5.4.16-43.el7_4.1 for package: php-devel-5.4.16-43.el7_4.1.x86_64
---> Package php-cli.x86_64 0:7.2.3-2.el7.remi will be an update
---> Package php-common.x86_64 0:5.4.16-43.el7_4.1 will be updated
--> Processing Dependency: php(api) = 20100412-64 for package: php-pecl-apcu-4.0.11-1.el7.x86_64
--> Processing Dependency: php(api) = 20100412-64 for package: php-pecl-ssh2-0.12-1.el7.x86_64
--> Processing Dependency: php(api) = 20100412-64 for package: php-mcrypt-5.4.16-7.el7.x86_64
--> Processing Dependency: php(api) = 20100412-64 for package: php-pecl-mongo-1.6.14-1.el7.x86_64
--> Processing Dependency: php(zend-abi) = 20100525-64 for package: php-pecl-apcu-4.0.11-1.el7.x86_64
--> Processing Dependency: php(zend-abi) = 20100525-64 for package: php-pecl-ssh2-0.12-1.el7.x86_64
--> Processing Dependency: php(zend-abi) = 20100525-64 for package: php-mcrypt-5.4.16-7.el7.x86_64
--> Processing Dependency: php(zend-abi) = 20100525-64 for package: php-pecl-mongo-1.6.14-1.el7.x86_64
--> Processing Dependency: php-json(x86-64) = 7.2.3-2.el7.remi for package: php-common-7.2.3-2.el7.remi.x86_64
--> Processing Dependency: php-common(x86-64) = 5.4.16-43.el7_4.1 for package: php-soap-5.4.16-43.el7_4.1.x86_64
--> Processing Dependency: php-common(x86-64) = 5.4.16-43.el7_4.1 for package: php-pdo-5.4.16-43.el7_4.1.x86_64
--> Processing Dependency: php-common(x86-64) = 5.4.16-43.el7_4.1 for package: php-mbstring-5.4.16-43.el7_4.1.x86_64
--> Processing Dependency: php-common(x86-64) = 5.4.16-43.el7_4.1 for package: php-gd-5.4.16-43.el7_4.1.x86_64
--> Processing Dependency: php-common(x86-64) = 5.4.16-43.el7_4.1 for package: php-process-5.4.16-43.el7_4.1.x86_64
--> Processing Dependency: php-common(x86-64) = 5.4.16-43.el7_4.1 for package: php-ldap-5.4.16-43.el7_4.1.x86_64
--> Processing Dependency: php-common(x86-64) = 5.4.16-43.el7_4.1 for package: php-xml-5.4.16-43.el7_4.1.x86_64
---> Package php-common.x86_64 0:7.2.3-2.el7.remi will be an update
--> Running transaction check
---> Package php-common.x86_64 0:5.4.16-43.el7_4.1 will be updated
--> Processing Dependency: php(api) = 20100412-64 for package: php-pecl-mongo-1.6.14-1.el7.x86_64
--> Processing Dependency: php(zend-abi) = 20100525-64 for package: php-pecl-mongo-1.6.14-1.el7.x86_64
---> Package php-devel.x86_64 0:5.4.16-43.el7_4.1 will be updated
---> Package php-devel.x86_64 0:7.2.3-2.el7.remi will be an update
---> Package php-gd.x86_64 0:5.4.16-43.el7_4.1 will be updated
---> Package php-gd.x86_64 0:7.2.3-2.el7.remi will be an update
--> Processing Dependency: gd-last(x86-64) >= 2.1.1 for package: php-gd-7.2.3-2.el7.remi.x86_64
--> Processing Dependency: libgd.so.3()(64bit) for package: php-gd-7.2.3-2.el7.remi.x86_64
---> Package php-json.x86_64 0:7.2.3-2.el7.remi will be installed
---> Package php-ldap.x86_64 0:5.4.16-43.el7_4.1 will be updated
---> Package php-ldap.x86_64 0:7.2.3-2.el7.remi will be an update
---> Package php-mbstring.x86_64 0:5.4.16-43.el7_4.1 will be updated
---> Package php-mbstring.x86_64 0:7.2.3-2.el7.remi will be an update
---> Package php-mcrypt.x86_64 0:5.4.16-7.el7 will be obsoleted
---> Package php-pdo.x86_64 0:5.4.16-43.el7_4.1 will be updated
--> Processing Dependency: php-pdo(x86-64) = 5.4.16-43.el7_4.1 for package: php-odbc-5.4.16-43.el7_4.1.x86_64
--> Processing Dependency: php-pdo(x86-64) = 5.4.16-43.el7_4.1 for package: php-mysql-5.4.16-43.el7_4.1.x86_64
---> Package php-pdo.x86_64 0:7.2.3-2.el7.remi will be an update
---> Package php-pecl-apcu.x86_64 0:4.0.11-1.el7 will be updated
---> Package php-pecl-apcu.x86_64 0:5.1.11-1.el7.remi.7.2 will be an update
---> Package php-pecl-mcrypt.x86_64 0:1.0.1-4.el7.remi.7.2 will be obsoleting
---> Package php-pecl-ssh2.x86_64 0:0.12-1.el7 will be updated
---> Package php-pecl-ssh2.x86_64 0:1.1.2-1.el7.remi.7.2 will be an update
---> Package php-process.x86_64 0:5.4.16-43.el7_4.1 will be updated
---> Package php-process.x86_64 0:7.2.3-2.el7.remi will be an update
---> Package php-soap.x86_64 0:5.4.16-43.el7_4.1 will be updated
---> Package php-soap.x86_64 0:7.2.3-2.el7.remi will be an update
---> Package php-xml.x86_64 0:5.4.16-43.el7_4.1 will be updated
---> Package php-xml.x86_64 0:7.2.3-2.el7.remi will be an update
--> Running transaction check
---> Package gd-last.x86_64 0:2.2.5-1.el7.remi will be installed
---> Package php-common.x86_64 0:5.4.16-43.el7_4.1 will be updated
--> Processing Dependency: php(api) = 20100412-64 for package: php-pecl-mongo-1.6.14-1.el7.x86_64
--> Processing Dependency: php(zend-abi) = 20100525-64 for package: php-pecl-mongo-1.6.14-1.el7.x86_64
---> Package php-mysql.x86_64 0:5.4.16-43.el7_4.1 will be obsoleted
---> Package php-mysqlnd.x86_64 0:7.2.3-2.el7.remi will be obsoleting
---> Package php-odbc.x86_64 0:5.4.16-43.el7_4.1 will be updated
---> Package php-odbc.x86_64 0:7.2.3-2.el7.remi will be an update
--> Finished Dependency Resolution
Error: Package: php-pecl-mongo-1.6.14-1.el7.x86_64 (@epel)
Requires: php(zend-abi) = 20100525-64
Removing: php-common-5.4.16-43.el7_4.1.x86_64 (@updates)
php(zend-abi) = 20100525-64
Updated By: php-common-7.2.3-2.el7.remi.x86_64 (remi-php72)
php(zend-abi) = 20170718-64
Available: php-common-5.4.16-42.el7.x86_64 (base)
php(zend-abi) = 20100525-64
Available: php-common-5.4.16-43.el7_4.x86_64 (updates)
php(zend-abi) = 20100525-64
Available: php-common-7.2.2-1.el7.remi.x86_64 (remi-php72)
php(zend-abi) = 20170718-64
Error: Package: php-pecl-mongo-1.6.14-1.el7.x86_64 (@epel)
Requires: php(api) = 20100412-64
Removing: php-common-5.4.16-43.el7_4.1.x86_64 (@updates)
php(api) = 20100412-64
Updated By: php-common-7.2.3-2.el7.remi.x86_64 (remi-php72)
php(api) = 20170718-64
Available: php-common-5.4.16-42.el7.x86_64 (base)
php(api) = 20100412-64
Available: php-common-5.4.16-43.el7_4.x86_64 (updates)
php(api) = 20100412-64
Available: php-common-7.2.2-1.el7.remi.x86_64 (remi-php72)
php(api) = 20170718-64
You could try using --skip-broken to work around the problem
You could try running: rpm -Va --nofiles --nodigest
How do I resolve the dependency issues in order to get PHP 7.2.3 up and running?