( mixed key, string &out [, string passphrase [, array configargs]] )
key as a PEM encoded string and stores it into
out (which is passed by reference).
The key is optionally protected by passphrase.
configargs can be used to fine-tune the export
process by specifying and/or overriding options for the openssl
configuration file. See openssl_csr_new() for more
information about configargs.
如果成功则返回 TRUE，失败则返回 FALSE。
You need to have a valid openssl.cnf installed for
this function to operate correctly.
See the notes under the installation
section for more information.