what is base64
You may have seen a string such as "YXNkZmZkc2FhYWFhZGRkZWY=" before. Some of you will recognize this as base64. Base64 is an encoding format used to represent binary data as text. It is commonly used in MIME email formats for things such as attachments.
In php, base64 funcitons are readily available for use.
base64_encode($data) - encodes to base64
base64_decode($data) - decodes from base64
Typically base64 encoded data takes a third more space to store than the original, as the data is encoded to a string versus just being stored as binary. If you are sending email attachments from your app, you will need to base64 encode the attachment as text and format the email accordingly.