get_schema.php

<?php
/**
 * Get the schema definition of a table, or the whole database schema.
 *
 *
 * @param $table The name of the table. If not given, the schema of all tables is returned.
 * @param $rebuild If true, the schema will be rebuilt instead of retrieved from the cache.
 */
function get_schema($table = NULL, $rebuild = FALSE) {
  static $schema = array();

  if (empty($schema) || $rebuild) {
    // Try to load the schema from the cache table.
    if (!$rebuild && $cached = cache_get('schema')) {
      $schema = $cached['data'];
    }
    // Otherwise, rebuild the schema cache.
    else {
      $schema = array();
      $query1 = "SHOW TABLES FROM '$db_name'";
      while($result = fetch_assoc($query1)){
          $query = "SHOW COLUMNS FROM '$result['table']'";
          $tmp = fetch_assoc($query);
          $schema[$table] = $tmp[0];;
      }
      //save the schema back to the cache table
      //upsert into cache where cid = 'schema' set data = $schema, created = now();
      cache_set('schema', $schema);
    }
  }

  if (!isset($table)) {
    return $schema;
  }
  elseif (isset($schema[$table])) {
    return $schema[$table];
  }
  else {
    return FALSE;
  }
}