I tried to install the php-ldap package on my machine but was not able to do so.
It shows missing dependencies error for php-common, but the said package is already installed and updated.
See the following screenshot:
Try:
yum clean all
yum update
yum install php-ldap
...in that order. If the yum update includes kernel or glibc updates, you should reboot after that step.
I have just resolved it by updating my PHP version from 5.4.37 to 5.6. That did the charm and was able to install php-ldap.