(PHP 4 >= 4.2.0, PHP 5)
openssl_pkey_export_to_file -- Gets an exportable representation of a key into a fileopenssl_pkey_export_to_file() saves an ascii-armoured (PEM encoded) rendition of key into the file named by outfilename. The key can be optionally protected by a 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.