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

xpath_escape.php

<?php
function xpathEscape($query, $default_delim = '"')
{
    if (strpos($query, $default_delim) === false)
        return $default_delim . $query . $default_delim;
    preg_match_all("#(?:('+)|[^']+)#", $query, $matches);
    list($parts, $apos) = $matches;
    foreach ($parts as $i => &$part) {
        $delim = $apos[$i] ? '"' : "'";
        $part = $delim . $part . $delim;
    }
    // concat() must have two or more parts
    if (count($parts)  == 1)
        $parts[] = $delim . $delim;
    return 'concat(' . implode(',', $parts) . ')';
}

I wrote a more efficient version: https://gist.github.com/thomasbachem/5076669

@thomasbachem, I don't think your version is necessarily more efficient. Implementing string searching in userland is typically less efficient. A more efficient alternative would be something along the lines of:

<?php
function xpathEscape($string)
{
    if (strpos($string, "'") === false) {
        return sprintf("'%s'", $string);
    }

    if (strpos($string, '"') === false) {
        return sprintf('"%s"', $string);
    }

    return sprintf(
      "concat('%s')", str_replace("'", "',\"'\",'", $string)
    );
}