openssl_pkey_export() exports
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. 成功回傳TRUE失敗回傳FALSE。
注: 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.