PHP Function to Minify HTML, CSS and JavaScript

php-html-css-js-minifier.php

<?php

/**
 * -----------------------------------------------------------------------------------------
 * Based on `https://github.com/mecha-cms/mecha-cms/blob/master/system/kernel/converter.php`
 * -----------------------------------------------------------------------------------------
 */

// HTML Minifier
function minify_html($input) {
    if(trim($input) === "") return $input;
    // Remove extra white-spaces between HTML attributes
    $input = preg_replace_callback('#<([^\/\s<>!]+)(?:\s+([^<>]*?)\s*|\s*)(\/?)>#s', function($matches) {
        return '<' . $matches[1] . preg_replace('#([^\s=]+)(\=([\'"]?)(.*?)\3)?(\s+|$)#s', ' $1$2', $matches[2]) . $matches[3] . '>';
    }, $input);
    // Minify inline CSS declarations
    if(strpos($input, ' style=') !== false) {
        $input = preg_replace_callback('#\s+style=([\'"]?)(.*?)\1(?=[\/\s>])#s', function($matches) {
            return ' style=' . $matches[1] . minify_css($matches[2]) . $matches[1];
        }, $input);
    }
    return preg_replace(
        array(
            // Remove HTML comments except IE comments
            '#\s*(<\!--(?=\[if).*?-->)\s*|\s*<\!--.*?-->\s*#s',
            // Do not remove white-space after image and
            // input tag that is followed by a tag open
            '#(<(?:img|input)(?:\/?>|\s[^<>]*?\/?>))\s+(?=\<[^\/])#s',
            // Remove two or more white-spaces between tags
            '#(<\!--.*?-->)|(>)\s{2,}|\s{2,}(<)|(>)\s{2,}(<)#s',
            // Proofing ...
            // o: tag open, c: tag close, t: text
            // If `<tag> </tag>` remove white-space
            // If `</tag> <tag>` keep white-space
            // If `<tag> <tag>` remove white-space
            // If `</tag> </tag>` remove white-space
            // If `<tag>    ...</tag>` remove white-spaces
            // If `</tag>    ...<tag>` remove white-spaces
            // If `<tag>    ...<tag>` remove white-spaces
            // If `</tag>    ...</tag>` remove white-spaces
            // If `abc <tag>` keep white-space
            // If `<tag> abc` remove white-space
            // If `abc </tag>` remove white-space
            // If `</tag> abc` keep white-space
            // TODO: If `abc    ...<tag>` keep one white-space
            // If `<tag>    ...abc` remove white-spaces
            // If `abc    ...</tag>` remove white-spaces
            // TODO: If `</tag>    ...abc` keep one white-space
            '#(<\!--.*?-->)|(<(?:img|input)(?:\/?>|\s[^<>]*?\/?>))\s+(?!\<\/)#s', // o+t | o+o
            '#(<\!--.*?-->)|(<[^\/\s<>]+(?:>|\s[^<>]*?>))\s+(?=\<[^\/])#s', // o+o
            '#(<\!--.*?-->)|(<\/[^\/\s<>]+?>)\s+(?=\<\/)#s', // c+c
            '#(<\!--.*?-->)|(<([^\/\s<>]+)(?:>|\s[^<>]*?>))\s+(<\/\3>)#s', // o+c
            '#(<\!--.*?-->)|(<[^\/\s<>]+(?:>|\s[^<>]*?>))\s+(?!\<)#s', // o+t
            '#(<\!--.*?-->)|(?!\>)\s+(<\/[^\/\s<>]+?>)#s', // t+c
            '#(<\!--.*?-->)|(?!\>)\s+(?=\<[^\/])#s', // t+o
            '#(<\!--.*?-->)|(<\/[^\/\s<>]+?>)\s+(?!\<)#s', // c+t
            '#(<\!--.*?-->)|(\/>)\s+(?!\<)#', // o+t
            // Replace `&nbsp;&nbsp;&nbsp;` with `&nbsp; &nbsp;`
            '#(?<=&nbsp;)(&nbsp;){2}#',
            // Proofing ...
            '#(?<=\>)&nbsp;(?!\s|&nbsp;|<\/)#',
            '#(?<=--\>)(?:\s|&nbsp;)+(?=\<)#'
        ),
        array(
            '$1',
            '$1&nbsp;',
            '$1$2$3$4$5',
            '$1$2&nbsp;', // o+t | o+o
            '$1$2', // o+o
            '$1$2', //c+c
            '$1$2$4', // o+c
            '$1$2', // o+t
            '$1$2', // t+c
            '$1$2 ', // t+o
            '$1$2 ', // c+t
            '$1$2 ', // o+t
            ' $1',
            ' ',
            ""
        ),
    trim($input));
}

// CSS Minifier => http://ideone.com/Q5USEF + improvement(s)
function minify_css($input) {
    if(trim($input) === "") return $input;
    return preg_replace(
        array(
            // Remove comments
            '#("(?:[^"\\\]++|\\\.)*+"|\'(?:[^\'\\\\]++|\\\.)*+\')|\/\*(?!\!)(?>.*?\*\/)#s',
            // Remove unused white-spaces
            '#("(?:[^"\\\]++|\\\.)*+"|\'(?:[^\'\\\\]++|\\\.)*+\'|\/\*(?>.*?\*\/))|\s*+;\s*+(})\s*+|\s*+([*$~^|]?+=|[{};,>~+]|\s*+-(?![0-9\.])|!important\b)\s*+|([[(:])\s++|\s++([])])|\s++(:)\s*+(?!(?>[^{}"\']++|"(?:[^"\\\]++|\\\.)*+"|\'(?:[^\'\\\\]++|\\\.)*+\')*+{)|^\s++|\s++\z|(\s)\s+#si',
            // Replace `0(cm|em|ex|in|mm|pc|pt|px|vh|vw|%)` with `0`
            '#(?<=[:\s])(0)(cm|em|ex|in|mm|pc|pt|px|vh|vw|%)#si',
            // Replace `:0 0 0 0` with `:0`
            '#:(0\s+0|0\s+0\s+0\s+0)(?=[;\}]|\!important)#i',
            // Replace `background-position:0` with `background-position:0 0`
            '#(background-position):0(?=[;\}])#si',
            // Replace `0.6` with `.6`, but only when preceded by `:`, `-`, `,` or a white-space
            '#(?<=[:\-,\s])0+\.(\d+)#s',
            // Minify string value
            '#(\/\*(?>.*?\*\/))|(?<!content\:)([\'"])([a-z_][a-z0-9\-_]*?)\2(?=[\s\{\}\];,])#si',
            '#(\/\*(?>.*?\*\/))|(\burl\()([\'"])([^\s]+?)\3(\))#si',
            // Minify HEX color code
            '#(?<=[:\-,\s]\#)([a-f0-6]+)\1([a-f0-6]+)\2([a-f0-6]+)\3#i',
            // Remove empty selectors
            '#(\/\*(?>.*?\*\/))|(^|[\{\}])(?:[^\s\{\}]+)\{\}#s'
        ),
        array(
            '$1',
            '$1$2$3$4$5$6$7',
            '$1',
            ':0',
            '$1:0 0',
            '.$1',
            '$1$3',
            '$1$2$4$5',
            '$1$2$3',
            '$1$2'
        ),
    trim($input));
}

// JavaScript Minifier
function minify_js($input) {
    if(trim($input) === "") return $input;
    return preg_replace(
        array(
            // '#(?<!\\\)\\\\\"#',
            // '#(?<!\\\)\\\\\'#',
            // Remove comments
            '#\s*("(?:[^"\\\]++|\\\.)*+"|\'(?:[^\'\\\\]++|\\\.)*+\')\s*|\s*\/\*\s*(?!\!|@cc_on)(?>[\s\S]*?\*\/)\s*|\s*(?<![\:\=])\/\/.*[\n\r]*#',
            // Remove unused white-space characters outside the string and regex
            '#("(?:[^"\\\]++|\\\.)*+"|\'(?:[^\'\\\\]++|\\\.)*+\'|\/\*(?>.*?\*\/)|\/(?!\/)[^\n\r]*?\/(?=[\.,;]|[gimuy]))|\s*([+\-\=\/%\(\)\{\}\[\]<>\|&\?\!\:;\.,])\s*#s',
            // Remove the last semicolon
            '#;+\}#',
            // Replace `true` with `!0`
            // '#\btrue\b#',
            // Replace `false` with `!1`
            // '#\bfalse\b#',
            // Minify object attribute except JSON attribute. From `{'foo':'bar'}` to `{foo:'bar'}`
            '#([\{,])([\'])(\d+|[a-z_][a-z0-9_]*)\2(?=\:)#i',
            // --ibid. From `foo['bar']` to `foo.bar`
            '#([a-z0-9_\)\]])\[([\'"])([a-z_][a-z0-9_]*)\2\]#i'
        ),
        array(
            // '\\u0022',
            // '\\u0027',
            '$1',
            '$1$2',
            '}',
            // '!0',
            // '!1',
            '$1$3',
            '$1.$3'
        ),
    trim($input));
}