PHP supports the "data: stream wrapper" natively, so you don't have to do ugly string manipulation to get, for example, the data from a string such as data://text/plain;base64,SSBsb3ZlIFBIUAo= and then write it to a file. Instead, you can do this:
$string = 'data://text/plain;base64,SSBsb3ZlIFBIUAo=';
$source = fopen($string, 'r');
$destination = fopen('myfile.txt', 'w');
stream_copy_to_stream($source, $destination);
fclose($source);
fclose($destination);
$source = fopen($string, 'r');
$destination = fopen('myfile.txt', 'w');
stream_copy_to_stream($source, $destination);
fclose($source);
fclose($destination);
You can also read the data into a string by simply doing this:
$data = file_get_contents('data://text/plain;base64,SSBsb3ZlIFBIUAo=');
Here is the relevant documentation, and you can see other supported wrappers (e.g. rar://).