Minify JavaScript and CSS Files

footer.php

<script>
    <?php 
        echo minifyJS([
            'path/to/a.js',
            'path/to/b.js'
        ]);
    ?>
</script>

header.php

<style>
    <?php 
        echo minifyCSS([
            'path/to/a.css',
            'path/to/b.css'
        ]);
    ?>
</style>

minify.php

<?php

/**
 * Concatenate an array of files into a string
 *
 * @param $files
 * @return string
 */
function concatenateFiles($files)
{
    $buffer = '';

    foreach($files as $file) {
        $buffer .= file_get_contents(__DIR__ . '/' . $file);
    }

    return $buffer;
}

/**
 * @param $files
 * @return mixed|string
 */
function minifyCSS($files)
{
    $buffer = concatenateFiles($files);

    $buffer = preg_replace('!/\*[^*]*\*+([^/][^*]*\*+)*/!', '', $buffer);
    $buffer = str_replace(["\r\n","\r","\n","\t",'  ','    ','     '], '', $buffer);
    $buffer = preg_replace(['(( )+{)','({( )+)'], '{', $buffer);
    $buffer = preg_replace(['(( )+})','(}( )+)','(;( )*})'], '}', $buffer);
    $buffer = preg_replace(['(;( )+)','(( )+;)'], ';', $buffer);

    return $buffer;
}

/**
 * @param $files
 * @return mixed|string
 */
function minifyJS($files) {
    $buffer = concatenateFiles($files);

    $buffer = preg_replace("/((?:\/\*(?:[^*]|(?:\*+[^*\/]))*\*+\/)|(?:\/\/.*))/", "", $buffer);
    $buffer = str_replace(["\r\n","\r","\t","\n",'  ','    ','     '], '', $buffer);
    $buffer = preg_replace(['(( )+\))','(\)( )+)'], ')', $buffer);

    return $buffer;
}