Returns a positive key resource identifier on success,
or FALSE on error.
openssl_get_privatekey() parses key and prepares it for use by other
functions. key can be one
of the following:
a string having the format
file://path/to/file.pem. The named file must contain
a PEM encoded certificate/private key (it may contain
both).
A PEM formatted private key.
The optional parameter
passphrase must be used if the specified key is
encrypted (protected by a passphrase).