Backend PHP PBX Developer

About MixvoipMixvoip is a Luxembourg-based company providing cloud telephony, smart networking, and high-speed internet services. We build and operate communication systems that businesses rely on every day. We are looking for a developer who wants to work close to telephony infrastructure and help improve the platform behind our cloud PBX services. Your level of experience is not the deciding factor. We are open to junior developers who want to grow into the role as well as experienced developers who can take ownership quickly and help shape the platform. About the roleYou will join our PBX development team and work on the systems that control call routing, device provisioning, configuration generation, and telephony automation. This is not a traditional web development role. There is no frontend, UI, or CSS work. Most of your work will involve backend services, CLI tools, scheduled jobs, APIs, configuration files, and direct interaction with our VoIP infrastructure. You will use PHP and Linux to develop and maintain features for our PBX platform. Depending on your experience, you may start with smaller, well-defined tasks and grow into more complex responsibilities, or you may take ownership of larger areas from the beginning. This role requires regular on-site presence at our office in Luxembourg and is not a remote position. What you will doDevelop and maintain features for our cloud PBX platformImplement call-routing rules and telephony configurationGenerate PBX and device configuration filesAutomate the provisioning of Yealink, Gigaset, and Grandstream devicesIntegrate internal systems and external telecom APIsBuild CLI tools, background workers, and scheduled jobsMaintain configuration templates using TwigInvestigate call-flow, provisioning, and integration issuesWork with logs to troubleshoot telephony problemsDocument PBX behaviour, code, and operational workflowsImprove the reliability and maintainability of the platform What we are looking forWe are interested in both potential and experience. You do not need to match every point. Knowledge of PHP or another backend programming languageComfort working in a Linux environmentUnderstanding of APIs, databases, JSON, and structured dataInterest in VoIP, telephony, networking, or infrastructureA methodical approach to debugging and problem-solvingClear communication and a collaborative attitudeWillingness to learn unfamiliar systemsAbility to work regularly from our Luxembourg officeFor junior candidates, internships, apprenticeships, school projects, open-source work, home labs, and personal projects all count. For experienced candidates, we value ownership, system design, production troubleshooting, performance awareness, and the ability to improve existing systems. Useful experiencePrevious experience with any of the following is helpful, but not required: SIPAsteriskPBX systemsCall routing and dial plansVoIP device provisioningTwig configuration templatesDockerCron jobs and background workersIP networking, routing, DNS, NAT, and firewallsTelecom vendor APIsMonitoring and troubleshooting production systemsJunior candidates are not expected to know all of this already. Senior candidates are not expected to have worked with our exact technology stack. How the role adapts to your levelIf you are earlier in your careerYou will receive guidance, learn how the platform works, and begin with manageable tasks such as: Updating configuration templatesFixing provisioning issuesImproving existing PHP scriptsInvestigating logsMaking small API changesTesting routing rulesWriting documentationAs your knowledge grows, you will gradually take ownership of larger PBX features and automation projects. If you are more experiencedYou may take ownership of larger technical areas, including: Designing new PBX capabilitiesImproving platform architectureLeading complex integrationsStrengthening reliability and observabilityReviewing code and technical approachesMentoring less experienced developersHelping define engineering standards and long-term improvementsWhat will make you stand outExperience with SIP, Asterisk, FreePBX, Kamailio, 3CX, or similar systemsStrong PHP and Linux experienceExperience running production backend or infrastructure systemsPersonal projects involving networking, telephony, automation, or self-hostingExperience with Docker, servers, routers, or home labsStrong troubleshooting and documentation habitsPractical use of AI coding tools in your daily workflowGenuine curiosity about how phone calls are routed and connectedA new way to apply: join Mixvoip’s success storyJoin Mixvoip and you won’t just be connecting businesses to high-speed internet, fiber, satellite, phone, or mobile networks, you’ll be connecting people, forging relationships, and making a real difference in our story. So, if you’re prepared to embark on an engaging journey and play a pivotal role in Mixvoip’s saga, here’s an unconventional route to apply We invite you to record a brief presentation video with your smartphone. Share why you’re drawn to this role or pose any questions or doubts you might have. It’s about keeping the conversation open and engaging! Please remember to attach your CV in PDF format too. Instead of a conventional cover letter, we’d like you to employ an AI of your choice. This not only mirrors our technology-focused approach, but it also allows you to showcase your adaptability to new tools. It’s less about the letter, more about your interaction with AI that we’re keen on. How to applySend us: Your CV in PDF formatA few sentences explaining why PBX and VoIP development interest youA short introduction video is welcome, but optional. You may also use an AI tool to help prepare your application, although this is not required. We care more about your ability, curiosity, and motivation than about your job title or number of years of experience. 💡 Whether you are starting your career or bringing years of experience, we want to hear from you.PS: Want to know who you’ll be journeying with? Meet me, Christophe LauresI’m 33 years old and have been part of Mixvoip for the past 10 years. Today, I lead the development of our PBX platform, working with the team to create the best possible experience for our customers. My main focus is driving the evolution of our newest PBX system so that our customers always have a reliable and versatile communication tool they can depend on. I enjoy solving complex challenges and finding clean, practical solutions that make a real difference. I’ve always been passionate about computers and technology, which is what originally led me into this field. Outside of work, I enjoy spending time outdoors. You’ll often find me hiking with my wife and our dog, recharging and getting ready for the next technical challenge. And on rainy days, I’m usually at home playing computer games.