HTML Compressor with regex
See: https://stackoverflow.com/a/6225706/736079

For comments on enabling content compression for your HTML pages, that usually is enough to reduce the payload by more than 50%.

You can also make use of output buffering and combine it with the HTMLMinify function:



&lt;?php
function sanitize_output($content) {
     $content = Minify_HTML::minify($content);
}

ob_start("sanitize_output");
?&gt;


See: https://github.com/mrclay/minify/blob/master/min/lib/Minify/HTML.php

This still uses Regex at the core, which is still not ideal, but it has been tested by a larger audience and looks quite solid (test to make sure). If you are hosting on IIS, you might be able to use a .NET HttpModule or an ISAPI filter as well. This isn't limited to PHP only, sometimes the Web Server itself has plugins that can help you, like Apache's mod_pagespeed.