I have the following php code: 

```
stream_context_set_option($ctx, 'ssl', 'local_cert', 'file.pem');  

```

and I'm trying to do this:

```
stream_context_set_option($ctx, 'ssl', 'local_cert', '$var.pem');  

```

but it is not accessing the .pem file correctly when I do it that way.

How do I add a variable and append .pem to the end of it in this scenario?