WeMakeScholars interview questions

How do you declare a variable in PHP?

They asked me my introduction and next they started asking me questions about my project and how i handle the database and how else can i do it to make it more efficient. They asked me how openai can be useful for we make scholars and how do we make it efficient(parameters to count on the people who need the services) and few sql questions (average to hard), iam not so comfortable or expert in sql so i lost the interview.