Function to escape single and double quotes in XPath queries using PHP

xpath_escape.php

<?php
    function xpathEscape($query,$default_delim = '"')
    {   

        if((strpos($query,'\'') !== FALSE) ||
           (strpos($query,'"') !== FALSE))
        {   
            $quotechars = array('\'','"');
            $parts = array();
            $current_part = '';

            foreach(str_split($query) as $character)
            {   
                if(in_array($character,$quotechars))
                {   
                    $parts[] = '\''.$current_part.'\'';

                    if($character == '\'')
                        $parts[] = '"'.$character.'"';
                    else
                        $parts[] = '\''.$character.'\'';

                    $current_part = '';
                }

                else
                    $current_part .= $character;
            }

            if($current_part)
                $parts[] = '\''.$current_part.'\'';

            $ret = 'concat('.implode(',',$parts).')';
        }

        else
            $ret = $default_delim.$query.$default_delim;

        return $ret;
    }