minify_css.php

<?php

function minify_css( $buffer ) {
    if( trim( $buffer ) === "") return $buffer;

    // Remove comments
    $buffer = preg_replace('!/\*[^*]*\*+([^/][^*]*\*+)*/!', '', $buffer);

    // Remove whitespace
    $buffer = preg_replace(array('/\s{2,}/', '/[\t\n]/'), ' ', $buffer);

    // Remove space after colons
    $buffer = str_replace(': ', ':', $buffer);

    // Remove space near commas
    $buffer = str_replace(', ', ',', $buffer);
    $buffer = str_replace(' ,', ',', $buffer);

    // Remove space near brackets
    $buffer = str_replace('{ ', '{', $buffer);
    $buffer = str_replace('} ', '}', $buffer);
    $buffer = str_replace(' {', '{', $buffer);
    $buffer = str_replace(' }', '}', $buffer);

    // Remove last dot with comma
    $buffer = str_replace(';}', '}', $buffer);

    return $buffer;
}

?>