Trim unnecessary whitespace from an HTML file or ERB template.

trimwhitespace.php

<?php

/**
 * Trim unnecessary whitespace from an HTML file or ERB template.
 *
 * This is taken directly from Smarty 3.1.7 (http://www.smarty.net):
 *   libs/plugins.outfilter.trimwhitespace.php
 *
 * Changes:
 *   - Removed argument "Smarty_Internal_Template $smarty".
 *   - Added ERB "<%" and "<%=" to "capture html elements not to be messed with".
 */
function trimwhitespace($source)
{
    $store = array();
    $_store = 0;
    $_offset = 0;

    // Unify Line-Breaks to \n
    $source = preg_replace("/\015\012|\015|\012/", "\n", $source);

    // capture Internet Explorer Conditional Comments
    if (preg_match_all('#<!--\[[^\]]+\]>.*?<!\[[^\]]+\]-->#is', $source, $matches, PREG_OFFSET_CAPTURE | PREG_SET_ORDER)) {
        foreach ($matches as $match) {
            $store[] = $match[0][0];
            $_length = strlen($match[0][0]);
            $replace = '@!@SMARTY:' . $_store . ':SMARTY@!@';
            $source = substr_replace($source, $replace, $match[0][1] - $_offset, $_length);

            $_offset += $_length - strlen($replace);
            $_store++;
        }
    }

    // Strip all HTML-Comments
    $source = preg_replace( '#<!--.*?-->#ms', '', $source );

    // capture html elements not to be messed with
    $_offset = 0;
    if (preg_match_all('#<(%|%=|script|pre|textarea)[^>]*>.*?</\\1>#is', $source, $matches, PREG_OFFSET_CAPTURE | PREG_SET_ORDER)) {
        foreach ($matches as $match) {
            $store[] = $match[0][0];
            $_length = strlen($match[0][0]);
            $replace = '@!@SMARTY:' . $_store . ':SMARTY@!@';
            $source = substr_replace($source, $replace, $match[0][1] - $_offset, $_length);

            $_offset += $_length - strlen($replace);
            $_store++;
        }
    }

    $expressions = array(
        // replace multiple spaces between tags by a single space
        // can't remove them entirely, becaue that might break poorly implemented CSS display:inline-block elements
        '#(:SMARTY@!@|>)\s+(?=@!@SMARTY:|<)#s' => '\1 \2',
        // remove spaces between attributes (but not in attribute values!)
        '#(([a-z0-9]\s*=\s*(["\'])[^\3]*?\3)|<[a-z0-9_]+)\s+([a-z/>])#is' => '\1 \4',
        // note: for some very weird reason trim() seems to remove spaces inside attributes.
        // maybe a \0 byte or something is interfering?
        '#^\s+<#Ss' => '<',
        '#>\s+$#Ss' => '>',
    );

    $source = preg_replace( array_keys($expressions), array_values($expressions), $source );
    // note: for some very weird reason trim() seems to remove spaces inside attributes.
    // maybe a \0 byte or something is interfering?
    // $source = trim( $source );

    // capture html elements not to be messed with
    $_offset = 0;
    if (preg_match_all('#@!@SMARTY:([0-9]+):SMARTY@!@#is', $source, $matches, PREG_OFFSET_CAPTURE | PREG_SET_ORDER)) {
        foreach ($matches as $match) {
            $store[] = $match[0][0];
            $_length = strlen($match[0][0]);
            $replace = array_shift($store);
            $source = substr_replace($source, $replace, $match[0][1] + $_offset, $_length);

            $_offset += strlen($replace) - $_length;
            $_store++;
        }
    }

    return $source;
}

// errors as exceptions
function exception_error_handler($errno, $errstr, $errfile, $errline ) {
    throw new ErrorException($errstr, 0, $errno, $errfile, $errline);
}
set_error_handler("exception_error_handler");

// trim whitespace
if (empty($argv[1]) || empty($argv[2])) {
  die("Usage: php trimwhitespace.php <in_filename> <out_filename>\n");
}
$source = file_get_contents($argv[1]);
file_put_contents($argv[2], trimwhitespace($source));