Add validation function in_db

Add validation function `in_db`. Usefull to checks the database to see if the given value exist. Can ignore records by field/value to filter (currently accept only one filter).

Author: kennylajara

system/Validation/Rules.php

@@ -139,6 +139,47 @@ public function greater_than_equal_to(string $str = null, string $min, array $da
 
 	//--------------------------------------------------------------------
 
+	/**
+	 * Checks the database to see if the given value exist.
+	 * Can ignore records by field/value to filter (currently
+	 * accept only one filter).
+	 *
+	 * Example:
+	 *    in_db[table.field,where_field,where_value]
+	 *    in_db[menu.id,active,1]
+	 *
+	 * @param string $str
+	 * @param string $field
+	 * @param array  $data
+	 *
+	 * @return boolean
+	 */
+	public function in_db(string $str = null, string $field, array $data): bool
+	{
+		// Grab any data for exclusion of a single row.
+		list($field, $where_field, $where_value) = array_pad(explode(',', $field), 3, null);
+
+		// Break the table and field apart
+		sscanf($field, '%[^.].%[^.]', $table, $field);
+
+		$db = Database::connect($data['DBGroup'] ?? null);
+
+		$row = $db->table($table)
+				  ->select('1')
+				  ->where($field, $str)
+				  ->limit(1);
+
+		if (! empty($where_field) && ! empty($where_value))
+		{
+			$row = $row->where($where_field, $where_value);
+		}
+
+		return (bool) ($row->get()
+						->getRow() !== null);
+	}
+
+	//--------------------------------------------------------------------
+
 	/**
 	 * Value should be within an array of values
 	 *