This procedural function will tell you if the table you are looking for is found within your currently selected MySQL database. Optionally, it will also determine if a column exists within the specified table. You can even pass the a value as the optional third parameter to see if the field’s value is also what you expect.

function match_table_field($table, $field = NULL, $value = NULL) {
   $table = mysql_escape_string($table);
   $query = mysql_query("SHOW TABLES LIKE '{$table}'");
   if (mysql_num_rows($query)) {
      if (empty($field)) {
         return TRUE;
      } else {
         $sql = "SELECT * FROM `{$table}`";
         if ($value) {
            $value = mysql_escape_string($value);
            $sql .= " WHERE `{$field}` = '{$value}'";
         }
         $query = mysql_query($sql);
         if (mysql_num_rows($query)) {
            if (empty($value)) {
               $row = mysql_fetch_array($query);
               return isset($row[$field]);
            } else {
               return TRUE;
            }
         }
      }
   }
   return FALSE;
}

I posted a similar suggestion in the Open Cart forums as a possible method to better automate Open Cart’s upgrade script.

Note: I converted the above example written for Open Cart to procedural PHP to reduce confusion and for the sake of simplicity 😉