I have installed PHP version 7 on my centOs.

Now I got an error says:

undefined function mb_internal_encoding()

So I decided to install php-mbstring (using yum install php-mbstring) but I face the following error:

Error: php70u-common conflicts with php-common-5.4.16-43.el7_4.x86_64

Error: php70u-json conflicts with php-common-5.4.16-43.el7_4.x86_64

But now when I install php-mbstring, it wants to install php-mbstring version 5.4.

How can I tell yum to download latest versions of php extensions and packages?