In addition to the front-end and back-end coding languages, you also need to choose a database to store and retrieve your information. The most-used open source databases are PostgreSQL and SQL. I tend to prefer the former. Of course, other very advanced and industry-specific databases are also available.
As a general rule, instead of focusing on the technology itself, I look at the technology mastered by the team’s most experienced developer. If my technical co-founder is a PHP guru, I would let him or her build the application in that language unless a specific stack was required.