I am trying to install yii2 on my Amazon Linux AMI instance, it requires the php-mbstring extension to work.
When I tried to run sudo yum install php-mbstring it returned this error:
Error: php56-common conflicts with php-common-5.3.29-1.8.amzn1.x86_64
Loaded plugins: priorities, update-motd, upgrade-helper
amzn-main/latest | 2.1 kB 00:00
amzn-updates/latest | 2.3 kB 00:00
2494 packages excluded due to repository priority protections
Resolving Dependencies
--> Running transaction check
---> Package php-mbstring.x86_64 0:5.3.29-1.8.amzn1 will be installed
--> Processing Dependency: php-common(x86-64) = 5.3.29-1.8.amzn1 for package: php-mbstring-5.3.29-1.8.amzn1.x86_64
--> Running transaction check
---> Package php-common.x86_64 0:5.3.29-1.8.amzn1 will be installed
--> Processing Conflict: php56-common-5.6.9-1.112.amzn1.x86_64 conflicts php-common < 5.5.22-1.98
--> Finished Dependency Resolution
Error: php56-common conflicts with php-common-5.3.29-1.8.amzn1.x86_64
You could try using --skip-broken to work around the problem
You could try running: rpm -Va --nofiles --nodigest
Thanks for your time in advance
Alex Andrei
It seems you have php 5.6 installed.
You need to install mbstring for that particular version of php.
Run sudo yum install php56-mbstring
After that it might be a good idea to restart apache (thanks! @hexicle),
using sudo service httpd restart
Victorio Berra
Amazon Linux AMI release 2017.09
sudo yum install php70-mysqlnd
sudo service httpd restart
来源：https://stackoverflow.com/questions/31190547/dependency-issue-trying-to-install-php-mbstring-on-ec2