Why does openssl_pkey_new() fail?

I'm very new to this. Why is openssl_pkey_new() returning false?

I am using XAMPP and there is a an OpenSSL under the Apahce\bin directory.

What obvious beginner mistake am I making? Maybe it's a matter of SSL configuration?

My goal is to write the two keys into two files.

Update: as suggested, I used openssl_error_string() and it says error:02001003:system library:fopen:No such process. It sounds like maybe OpenSSL isn't running or isn't in the path?? Any ideas?

Update: I put c:\xampp\php into the windows path, so that it could find libeay32.dlland restarted Apache.

Now I get error:2006D080:BIO routines:BIO_new_file:no such file. Any ideas?