Kubernetes php container can't seem to connect to mysql service

Question

Strange one, i have a php container with symfony, and a mysql pod that is attached to a service called mysql-service. I send the mysql connection details in the env variables on the php deployment.

Weirdly when symfony can't connect to the mysql pod using the service name.When i describe the php pod it says:

An exception occurred in driver: SQLSTATE[HY000] [2002] Connection refused 

I can see it's the name resolution:

getaddrinfo failed: Temporary failure in name resolution

If i change the deployment config so the DB_HOST env variable is that of another mysql server on the local network it connects just fine, and i know the mysql user and pass are correct as the mysql deployment and the php deployment both use the mysql secret file; i have also logged into the shell of the mysql pod and connected the database with the same user and pass no problem.

It looks like it's something about the mysql service itself.

Php deployment (some of it's removed as not relevant to my problem):

containers:
        - name: php
          lifecycle:
            postStart:
              exec:
                command: ["/bin/bash", "-c", "cd /usr/share/nginx/html && php bin/console cache:clear"]
          env:
            - name: APP_ENV
              value: "prod"
            - name: DB_NAME
              valueFrom:
                secretKeyRef:
                  name: mysql-secret
                  key: database
            - name: DB_USER
              valueFrom:
                secretKeyRef:
                  name: mysql-secret
                  key: username
            - name: DB_PASS
              valueFrom:
                secretKeyRef:
                  name: mysql-secret
                  key: password
            - name: DB_HOST
              value: "mysql-service"
            - name: DB_PORT
              value: "3306"
            
         
          imagePullPolicy: Always
          image: php-image-here
          ports:
            - containerPort: 9000
          

the mysql deployment and service:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: mysql-deployment
  labels:
    deploy: mysql
spec:
  replicas: 1
  selector:
    matchLabels:
      deploy: mysql
  template:
    metadata:
      labels:
        deploy: mysql
    spec:
      containers:
        - name: mysql
          imagePullPolicy: Always
          
          image: mysql-image-here
          ports:
            - containerPort: 3306
          volumeMounts:
            - mountPath: /var/lib/mysql
              name: mysql-volume
          env:
            - name: MYSQL_RANDOM_ROOT_PASSWORD
              value: "yes"
            - name: MYSQL_USER
              valueFrom:
                secretKeyRef:
                  name: mysql-secret
                  key: username
            - name: MYSQL_PASSWORD
              valueFrom:
                secretKeyRef:
                  name: mysql-secret
                  key: password
            - name: MYSQL_DATABASE
              valueFrom:
                secretKeyRef:
                  name: mysql-secret
                  key: database
      volumes:
        - name: mysql-volume
          hostPath:
            path: /data/mysql
            type: DirectoryOrCreate

---

apiVersion: v1
kind: Service
metadata:
  name: mysql-service
spec:
  selector:
    deploy: mysql
  ports:
    - protocol: TCP
      port: 3306
      targetPort: 3306

The service and the mysql pod are up and running:

NAME                                       READY   STATUS             RESTARTS        AGE
pod/backend-deployment-7d585fd8fd-9z5dp    1/2     CrashLoopBackOff   5 (2m54s ago)   7m9s
pod/mysql-deployment-7cb7999d98-blpzr      1/1     Running            0               50m

NAME                       TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)          AGE
service/backend-service    NodePort    10.97.250.92     <none>        80:30002/TCP     38m
service/kubernetes         ClusterIP   10.96.0.1        <none>        443/TCP          4d18h
service/mysql-service      ClusterIP   10.111.226.120   <none>        3306/TCP         50m