Here is a very simple stream wrapper which calls your callback function for reads:
<?php
class CallbackUrl
{
const WRAPPER_NAME = 'callback';
public $context;
private $_cb;
private $_eof = false;
private static $_isRegistered = false;
public static function getContext($cb)
{
if (!self::$_isRegistered) {
stream_wrapper_register(self::WRAPPER_NAME, get_class());
self::$_isRegistered = true;
}
if (!is_callable($cb)) return false;
return stream_context_create(array(self::WRAPPER_NAME => array('cb' => $cb)));
}
public function stream_open($path, $mode, $options, &$opened_path)
{
if (!preg_match('/^r[bt]?$/', $mode) || !$this->context) return false;
$opt = stream_context_get_options($this->context);
if (!is_array($opt[self::WRAPPER_NAME]) ||
!isset($opt[self::WRAPPER_NAME]['cb']) ||
!is_callable($opt[self::WRAPPER_NAME]['cb'])) return false;
$this->_cb = $opt[self::WRAPPER_NAME]['cb'];
return true;
}
public function stream_read($count)
{
if ($this->_eof || !$count) return '';
if (($s = call_user_func($this->_cb, $count)) == '') $this->_eof = true;
return $s;
}
public function stream_eof()
{
return $this->_eof;
}
}
class Test {
private $_s;
public function __construct($s)
{
$this->_s = $s;
}
public function read($count) {
return fread($this->_s, $count);
}
}
$t = new Test(fopen('/etc/services', 'r'));
$fd = fopen('callback://', 'r', false, CallbackUrl::getContext(array($t, 'read')));
while(($buf = fread($fd, 128)) != '') {
print $buf;
}
?>