I have been working on a social network for months and am quite tired of doing everything alone.I am only searching for people with knowledge in PHP, JavaScript and jQuery but can't find anybody.
I feel desperate.
I work in a startup on a similar project.
I would differentiate two types of projects from what you're saying: tech-related projects and innovation of use projects.
Tech-related projects
If the project is resolving a tech problem then I think @sergiuprt is right: you should consider making the project open-source. That way, you will build a community of developers (contributors) that will use your project to solve their own problems.
You can make the whole project open-source or just some part of it.
Github makes it easier with Pull Requests. People forks (copy) your project, do some work on their own copy, and then propose their work through a Pull Request. From there, you (as the project owner) can merge their code or discuss it and ask them to modify it to match your vision.
I'm not saying it's simple and will demands some work to set it up but in the long run, you're moving in the right way.
Innovation of use projects
Then building a community of developers around your project might be difficult and what you're looking for is help / employees more than contributors.
My startup falls into this category.
We managed to get help by designing our project into modules.
The core project is open-source, some modules too and some are not. Obviously, what makes our social network (the design, the business model, the community, the marketing, etc...) is private. Other developers use our core and our modules to build their own projects and contribute back:
Our mentor said to us something like three years ago: "Building a startup is a marathon, not a sprint" ;)
First question you should ask yourself here: What will those who work for you get in return and is it any value for them.
If it is for gaining personal experience and for your career portfolio, I'd suggest you to do it yourself so you can teach yourself the whole process of web development. Don't rush it, it's better to learn something than releasing an unfinished project.
As for recruiting people, either find people in person during meet-ups or conferences or join Slack and ask some of the communities.
Make sure to use your ideas somehow, else it would be a waste of time (and money if used any).
Alex Blattner
I am creating a new social network
Pēteris
Software Developer
You could recruit some first year undergrads at a university. Offer to mentor them and teach them some programming as they work on your project.
Another option is to participate in a weekend hackathon. At the hackathon I went to, people presented their project ideas and others could join them. If your idea is interesting, you could attract some interested developers to work on your project for a couple of days. If they like it, they may keep working with you after the hackathon.