(PHP 4 >= 4.2.0, PHP 5)
openssl_pkey_export -- Gets an exportable representation of a key into a stringopenssl_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. 如果成功则返回 TRUE，失败则返回 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.