Hello.
My name is Dmytro Nasyrov. I'm CTO at Pharos Production Inc.
Just a friendly advice - you can't update IPA or APK, only source code - force your previous developer to send you all required sources. If you don't have the source of your mobile apps, it's really bad. With PHP it's easier to update because PHP is a scripting language and the source(usually) is on the server. But we don't work with PHP and don't recommend this bunch of technologies to anyone.
And about us. We're Las Vegas based software company with development branches in Eastern Europe (Ukraine, Lithuania). We specialize on high-load systems, including custom distributed and decentralized technologies like blockchain, with all required infra - web front end, mobile apps, devOps etc. We use cutting-edge tools in our technology stack - Elixir, Erlang, ReactJS, Kotlin for Android, Swift for iOS, Kubernetes, Docker and Ansible for deployment into AWS, Azure or private servers. Also we provide development of distributed / decentralized projects on Ethereum - Smart Contracts and ICO.
Our rates are flexible: $20-$40/hr, we can provide you any amount of the required resource - from 1 week of a single developer, 40 hrs/week.
Let me know if you have any questions and you're welcome to look through our website, meet our team at LinkedIn or visit our development offices.
Looking forward to know more about your project.