- str_repeat: documentation ( source)
- stream_get_contents: documentation ( source)
- stream_filter_append: documentation ( source)
- fopen: documentation ( source)
<?php
$string = str_repeat("0123456789", 100);
$resource = fopen('data://text/plain,' . $string,'r');
stream_filter_append($resource, 'zlib.deflate', STREAM_FILTER_READ, 6);
$compressed = stream_get_contents($resource);
echo strlen($compressed);