utility functions: addQuotes and trimQuotes

// ----------------------------------------------------------------------------*
// strip quote marks from a string -- workout which quoutes are used
function trimQuotes($expr, $quoteChar='?')
{
    $exprChar = substr($expr, 0, 1);
    if (    $quoteChar === '?'
         && strpos('\'\"', $exprChar) !== false) {
        $quoteChar = $exprChar;
    }
    return  trim($expr, $quoteChar);
}

// ----------------------------------------------------------------------------*
// add double quote marks to a string check that it doesn't have them already.
function addQuotes($expr, $quotechar='"')
{
    if (substr($expr, 0, 1) != $quotechar) {
      return $quotechar . $expr . $quotechar;
    }
    else {
      return $expr;
    }
}