data://

When passing plain string without base64 encoding, do not forget to pass the string through URLENCODE(), because PHP automatically urldecodes all entities inside passed string (and therefore all + get lost, all % entities will be converted to the corresponding characters).

In this case, PHP is strictly compilant with the RFC 2397. Section 3 states that passes data should be either in base64 encoding or urlencoded.

VALID USAGE:
<?php
$fp = fopen('data:text/plain,'.urlencode($data), 'rb'); // urlencoded data
$fp = fopen('data:text/plain;base64,'.base64_encode($data), 'rb'); // base64 encoded data
?>

Demonstration of invalid usage:
<?php
$data = 'Günther says: 1+1 is 2, 10%40 is 20.';

$fp = fopen('data:text/plain,'.$data, 'rb'); // INVALID, never do this
echo stream_get_contents($fp);
// Günther says: 1 1 is 2, 10@ is 20. // ERROR

$fp = fopen('data:text/plain,'.urlencode($data), 'rb'); // urlencoded data
echo stream_get_contents($fp);
// Günther says: 1+1 is 2, 10%40 is 20. // OK

// Valid option 1: base64 encoded data
$fp = fopen('data:text/plain;base64,'.base64_encode($data), 'rb'); // base64 encoded data
echo stream_get_contents($fp);
// Günther says: 1+1 is 2, 10%40 is 20. // OK
?>

If you want to create a gd-image directly out of a sql-database-field you might want to use:

<?php
$jpegimage = imagecreatefromjpeg("data://image/jpeg;base64," . base64_encode($sql_result_array['imagedata']));
?>

this goes also for gif, png, etc using the correct "imagecreatefrom$$$"-function and mime-type.

Now PHP supports data: protocol w/out "//" like data:text/plain, not data://text/plain,

I tried it.