public function isUniqueValue($strTable, $strField, $varValue, $intId = null)
{
$strQuery = "SELECT * FROM {$strTable} WHERE {$strField}=?";
if ($intId !== null) {
$strQuery .= " AND id!=?";
}
$objUnique = $this->prepare($strQuery)->limit(1)->execute($varValue, $intId);
return $objUnique->numRows ? false : true;
}