base64_encode Encodes data with MIME base64 stringbase64_encode stringdata base64_encode returns data encoded with base64. This encoding is designed to make binary data survive transport through transport layers that are not 8-bit clean, such as mail bodies. Base64-encoded data takes about 33% more space than the original data. See also: base64_decode, chunk_split, RFC 2045 section 6.8.