How to read a single file inside a zip archive

Try using the zip:// wrapper:

$handle = fopen('zip://test.zip#test.txt', 'r'); 
$result="";
while (!feof($handle)) {
  $result .= fread($handle, 8192);
}
fclose($handle);
echo $result;

You can use file_get_contents too:

$result = file_get_contents('zip://test.zip#test.txt');
echo $result;