PHP Function to Minify HTML Output

minify-html-output.php

<?php
// start the output buffer 
  ob_start('compress_page');
?>
<!-- all html content here -->
<?php
// end the buffer, echo the page content
  ob_end_flush();

//  function that gets rid of tabs, line breaks, and extra spaces
function compress_page($buffer) {
// remove comments, tabs, spaces, newlines, etc.
$search = array(
  "/\/\*(.*?)\*\/|[\t\r\n]/s" => "",
  "/ +\{ +|\{ +| +\{/" => "{",
  "/ +\} +|\} +| +\}/" => "}",
  "/ +: +|: +| +:/" => ":",
  "/ +; +|; +| +;/" => ";",
  "/ +, +|, +| +,/" => ","
);
$buffer = preg_replace(array_keys($search), array_values($search), $buffer);
  return $buffer;
}

Taken from davidwalsh.name/php-output-buffers - updated function: see comment by Shaun.