I am currently working on a PHP project and I am struggling with `preg_match()` and regex regular expressions. I have read the documentation and some tutorials, but I still can't fully grasp it. I hope someone here can help me understand it better.
To give you some context, I am working on a form validation where I need to check if an input field contains only alphanumeric characters. From what I understand, `preg_match()` is the function to use for this task, along with a regex regular expression.
Could someone please explain to me how `preg_match()` and regex regular expressions work together? Specifically, how can I use them to validate if a string contains only alphanumeric characters?
I would also appreciate it if someone could provide an example of how to implement this validation in PHP, so I can see it in action.
Thank you in advance for your help!