Run an Ansible task only when the hostname contains a string

Below should do the trick:

- name: Install PHP Modules
  command: <command>
  with_dict: php_modules
  when: "'batch' in inventory_hostname"

Note you’ll have a couple of skipped hosts during playbook run.

inventory_hostname is one of Ansible’s “magic” variables:

Additionally, inventory_hostname is the name of the hostname as
configured in Ansible’s inventory host file. This can be useful for
when you don’t want to rely on the discovered hostname
ansible_hostname or for other mysterious reasons. If you have a long
FQDN, inventory_hostname_short also contains the part up to the first
period, without the rest of the domain.

Source: Ansible Docs – Magic variables