As said in comments your best option is create Kubernetes CronJobs.

If you don't want to expose you PHP functions, you can always use a container that execute commands in your PHP pods.

Here is an example that create a cronjob. This cronjob runs kubectl exec for every pod with label app=my-php, calling ls in each pod.

  apiVersion: batch/v1beta1
  kind: CronJob
  metadata:
    name: hello-cron
  spec:
    schedule: "*/1 * * * *"
    jobTemplate:
      spec:
        template:
          spec:
            containers:
            - name: kubectl
              image: lachlanevenson/k8s-kubectl
              command:
                - /bin/sh
                - -c
              args: 
                - kubectl get pod -l app=my-php -o jsonpath='{range .items[*]}{.metadata.name}{"\n"}{end}' | xargs -i kubectl exec {} ls
            restartPolicy: Never