[SOLVED] Some PHX explanation please

<?php
/**
 * @name TransAlias
 * @desc Handle the task of loading transliteration tables and applying them
 *      to a string for the purpose of creating a friendly URL alias.
 * @package modx
 * @subpackage modx.plugins.transalias
 * @author Olivier B. Deland
 * @license GNU General Public License
 */
class TransAlias {
    /**
     * name of the file to use for transliteration (without .php)
     * also used as array key
     *
     * @var string
     * @access private
     */
    var $_useTable;
    
    /**
     * hold conversion tables
     *
     * @var array
     * @access 
     */
    var $_tables = array ('named' => array (
            'quot' => '"','amp' => '&','lt' => '<','gt' => '>','OElig' => 'Œ','oelig' => 'œ','Scaron' => 'Š','scaron' => 'š',
            'Yuml' => 'Ÿ','circ' => 'ˆ','tilde' => '˜','ensp' => ' ','emsp' => ' ','thinsp' => ' ','zwnj' => '‌','zwj' => '‍',
            'lrm' => '‎','rlm' => '‏','ndash' => '–','mdash' => '—','lsquo' => '‘','rsquo' => '’','sbquo' => '‚','ldquo' => '“',
            'rdquo' => '”','bdquo' => '„','dagger' => '†','Dagger' => '‡','permil' => '‰','lsaquo' => '‹','rsaquo' => '›','euro' => '€',
            'fnof' => 'ƒ','Alpha' => 'Α','Beta' => 'Β','Gamma' => 'Γ','Delta' => 'Δ','Epsilon' => 'Ε','Zeta' => 'Ζ','Eta' => 'Η',
            'Theta' => 'Θ','Iota' => 'Ι','Kappa' => 'Κ','Lambda' => 'Λ','Mu' => 'Μ','Nu' => 'Ν','Xi' => 'Ξ','Omicron' => 'Ο',
            'Pi' => 'Π','Rho' => 'Ρ','Sigma' => 'Σ','Tau' => 'Τ','Upsilon' => 'Υ','Phi' => 'Φ','Chi' => 'Χ','Psi' => 'Ψ',
            'Omega' => 'Ω','alpha' => 'α','beta' => 'β','gamma' => 'γ','delta' => 'δ','epsilon' => 'ε','zeta' => 'ζ','eta' => 'η',
            'theta' => 'θ','iota' => 'ι','kappa' => 'κ','lambda' => 'λ','mu' => 'μ','nu' => 'ν','xi' => 'ξ','omicron' => 'ο',
            'pi' => 'π','rho' => 'ρ','sigmaf' => 'ς','sigma' => 'σ','tau' => 'τ','upsilon' => 'υ','phi' => 'φ','chi' => 'χ',
            'psi' => 'ψ','omega' => 'ω','thetasym' => 'ϑ','upsih' => 'ϒ','piv' => 'ϖ','bull' => '•','hellip' => '…','prime' => '′',
            'Prime' => '″','oline' => '‾','frasl' => '⁄','weierp' => '℘','image' => 'ℑ','real' => 'ℜ','trade' => '™','alefsym' => 'ℵ',
            'larr' => '←','uarr' => '↑','rarr' => '→','darr' => '↓','harr' => '↔','crarr' => '↵','lArr' => '⇐','uArr' => '⇑',
            'rArr' => '⇒','dArr' => '⇓','hArr' => '⇔','forall' => '∀','part' => '∂','exist' => '∃','empty' => '∅','nabla' => '∇',
            'isin' => '∈','notin' => '∉','ni' => '∋','prod' => '∏','sum' => '∑','minus' => '−','lowast' => '∗','radic' => '√',
            'prop' => '∝','infin' => '∞','ang' => '∠','and' => '∧','or' => '∨','cap' => '∩','cup' => '∪','int' => '∫',
            'there4' => '∴','sim' => '∼','cong' => '≅','asymp' => '≈','ne' => '≠','equiv' => '≡','le' => '≤','ge' => '≥',
            'sub' => '⊂','sup' => '⊃','nsub' => '⊄','sube' => '⊆','supe' => '⊇','oplus' => '⊕','otimes' => '⊗','perp' => '⊥',
            'sdot' => '⋅','lceil' => '⌈','rceil' => '⌉','lfloor' => '⌊','rfloor' => '⌋','lang' => '⟨','rang' => '⟩','loz' => '◊',
            'spades' => '♠','clubs' => '♣','hearts' => '♥','diams' => '♦','nbsp' => ' ','iexcl' => '¡','cent' => '¢','pound' => '£',
            'curren' => '¤','yen' => '¥','brvbar' => '¦','sect' => '§','uml' => '¨','copy' => '©','ordf' => 'ª','laquo' => '«',
            'not' => '¬','shy' => '­','reg' => '®','macr' => '¯','deg' => '°','plusmn' => '±','sup2' => '²','sup3' => '³',
            'acute' => '´','micro' => 'µ','para' => '¶','middot' => '·','cedil' => '¸','sup1' => '¹','ordm' => 'º','raquo' => '»',
            'frac14' => '¼','frac12' => '½','frac34' => '¾','iquest' => '¿','Agrave' => 'À','Aacute' => 'Á','Acirc' => 'Â','Atilde' => 'Ã',
            'Auml' => 'Ä','Aring' => 'Å','AElig' => 'Æ','Ccedil' => 'Ç','Egrave' => 'È','Eacute' => 'É','Ecirc' => 'Ê','Euml' => 'Ë',
            'Igrave' => 'Ì','Iacute' => 'Í','Icirc' => 'Î','Iuml' => 'Ï','ETH' => 'Ð','Ntilde' => 'Ñ','Ograve' => 'Ò','Oacute' => 'Ó',
            'Ocirc' => 'Ô','Otilde' => 'Õ','Ouml' => 'Ö','times' => '×','Oslash' => 'Ø','Ugrave' => 'Ù','Uacute' => 'Ú','Ucirc' => 'Û',
            'Uuml' => 'Ü','Yacute' => 'Ý','THORN' => 'Þ','szlig' => 'ß','agrave' => 'à','aacute' => 'á','acirc' => 'â','atilde' => 'ã',
            'auml' => 'ä','aring' => 'å','aelig' => 'æ','ccedil' => 'ç','egrave' => 'è','eacute' => 'é','ecirc' => 'ê','euml' => 'ë',
            'igrave' => 'ì','iacute' => 'í','icirc' => 'î','iuml' => 'ï','eth' => 'ð','ntilde' => 'ñ','ograve' => 'ò','oacute' => 'ó',
            'ocirc' => 'ô','otilde' => 'õ','ouml' => 'ö','divide' => '÷','oslash' => 'ø','ugrave' => 'ù','uacute' => 'ú','ucirc' => 'û',
            'uuml' => 'ü','yacute' => 'ý','thorn' => 'þ','yuml' => 'ÿ'
    ));

    /**
     * Swap named HTML entities with numeric entities.
     *
     * @see *deadlink*http://www.lazycat.org/software/html_entity_decode_full.phps
     */
    function convert_entity($matches, $destroy= true) {
         if (isset($this->$_tables['named'][$matches[1]]))
            return $this->$_tables['named'][$matches[1]];
        else
            return $destroy ? '' : $matches[0];
    }

    /**
     * return the value of a POSTed TV
     * TV may be used to override the default or hard-configured transliteration table
     *
     * @param string $tv name of Template Variable
     * @return value of TV in current POST operation or false if TV not found in POST
     */
    function getTVValue($tv) {
        $modx =& $GLOBALS['modx'];
        $additionalEncodings = array('-' => '%2D', '.' => '%2E', '_' => '%5F');
        $tvname = str_replace(array_keys($additionalEncodings), array_values($additionalEncodings), rawurlencode($tv));
        if(array_key_exists('tv'.$tvname, $_POST)) {
            include_once $GLOBALS['modx']->config['base_path'] . 'manager/includes/tmplvars.commands.inc.php';
            $val = $_POST['tv'.$tvname];
            $id = $_POST['id'];
            if($val == '@INHERIT' && empty($_POST['id']) && !empty($_POST['parent'])) {
                // we have to look at parent directly
                $id = $_POST['parent'];
                $parent = $modx->getPageInfo($_POST['parent'], 0, 'id,parent,published');
                $ptv = $modx->getTemplateVar($tv, '*', $parent['id'], $parent['published']);
                $val = $ptv['value'];
            }
            $return = ProcessTVCommand($val, $tv, $id);
    		return $return;
    	} else {
    		return false;
    	}
    }

    /**
     * load a transliteration table from a file and use it
     *
     * @param string $name
     * @return bool success
     */
    function loadTable($name) {
        if (empty($name) || !is_string($name)) {
            return false;
        }
        if (isset ($this->_tables[$name] )) {
            $this->_useTable = $name;
            return true;
        } else {
            $filePath = dirname(__FILE__).'/transliterations/'.$name.'.php';
            if (is_file($filePath)) {
                $this->_tables[$name] = include $filePath;
                if (is_array($this->_tables[$name]) && !empty($this->_tables[$name])) {
                    $this->_useTable = $name;
                    return true;
                } else {
                    return false;
                }
            } else {
                return false;
            }
        }
        return false;
    }

    /**
     * perform transliteration and clean up alias
     *
     * @param string $alias
     * @return string alias
     */
    function stripAlias($alias) {
        // Convert all named HTML entities to numeric entities
        $alias = preg_replace_callback('/&([a-zA-Z][a-zA-Z0-9]{1,7});/', array($this,'convert_entity'), $alias);
        
        // Convert all numeric entities to their actual character
        $alias = preg_replace('/&#x([0-9a-f]{1,7});/ei', 'chr(hexdec("\\1"))', $alias);
        $alias = preg_replace('/&#([0-9]{1,7});/e', 'chr("\\1")', $alias);
        
        if (!empty($this->_useTable)) {
            $alias = strtr($alias, $this->_tables[$this->_useTable]);
        }

        $alias = strip_tags($alias); // strip HTML
        $alias = preg_replace('/[^\.%A-Za-z0-9 _-]/', '', $alias); // strip non-alphanumeric characters
        // Edited to replace spaces with underscor not dash
		//$alias = preg_replace('/\s+/', '-', $alias); // convert white-space to dash
        $alias = preg_replace('/\s+/', '_', $alias); // convert white-space to dash		
        $alias = preg_replace('/-+/', '-', $alias);  // convert multiple dashes to one
        $alias = trim($alias, '-'); // trim excess
		$alias = preg_replace('[.html]', '', $alias); // remove .html if present
		$alias .= ".html"; // add it back
        return $alias;
    }

}
?>