Question

Is there any lightweight validation library available for PHP that easily can check if a specific string or value is valid for a known database type –

Something like this:

 if (is_MEDIUMINT($var)) {
      $this->db->insert($anothervar);
 }

Thanks!

Answer 1

The INFORMATION_SCHEMA database is part of the ANSI 2003 specification, so you could use that across any DB vendor that supports it (MySQL, Postgresql, SQLite, MSSQL 2k5+).

/*public static*/ function is_dbtype($table, $column, $type) {
    $db = (...)::getInstance(); // assuming PDO
    $sql = 'SELECT COLUMN_TYPE FROM INFORMATION_SCHEMA.COLUMNS '.
        'WHERE TABLE_NAME = :table AND COLUMN_NAME = :column';
    $st = $db->prepare($sql);
    $st->execute(array(':table' => $table, ':column' => $column));
    return ($type == $st->fetchColumn());
}

Change COLUMN_TYPE to DATA_TYPE if you just want “varchar” instead of “varchar(64)”. If you need more, there’s plenty: IS_NULLABLE, NUMERIC_PRECISION, CHARACTER_SET_NAME, etc.

(Not sure I’d use personally use this though, the is_* functions usually do enough without an extra database call. More importantly, info_schema holds the structure of every database on the server, so granting read permissions to it might (should) be a big deal. If you’re on a shared host you likely won’t have access to it at all.)

MySQL-only alternate: do similar but with DESCRIBE [table]. It’s pretty explicit though, you’ll have to fish out the “bigint” in “bigint(21) unsigned” yourself if that’s all you want.