VARIABLES FROM HTML TO FLASH VIA QUERY STRING
This tutorial is very similar to another tutorial elsewhere
on this site about Passing
Variables From HTML to Flash via FlashVars. The main
difference is in the syntax; and it is fairly minor. Also,
FlashVars only works with Flash Player 6 (that is Flash MX)
or newer. If you're only supporting Flash Player 6 or
newer, I recommend using FlashVars.
Note: ActionScript 3 user should go here after reding this tutorial for Action Script 3 way of accessing query strings.
Why and When to use Query String
Flash supports several methods of communicating to the outside world.
Some of the common methods are: loadVariables,
the XML object,
the FlashVars, and
the XMLSocket. With these
methods, you can retrieve parameters via an external file or
via CGI scripts. However, there is a less conventional
method, which is to use what is called the query string. This method is
practical but only suitable for simple situations such as
- The data to be passed is fairly simple. By simple,
I mean simple text (such as user name, filename, id, or cookie
- The data to be passed is not long. I recommend
less than 1024 characters. (The actual limit depends on
the browser and the server.)
- You don't care about the security of the data.
Query string is not secure. Any user can
easily see the content of the query string in the browser's
URL/Address bar; or by viewing the page source (as will be
shown later). Something like a password should NEVER
be passed via the query string. Let me say this
again: anything even
remotely sensitive should not be passed via the query
What is Query String?
Query string is the string that follows the "?"
sign within an URL. Below, is an URL followed by the query
The query string by itself (such as shown above) normally
is not very meaningful to
the end user. Most commonly, query string is used by CGI programs to retrieve data from HTML
forms. As an example, in the above case, suppose that the file mycgi.pl
is a CGI program, it will be able to retrieve these variable
and value pairs from the query string:
- message = hello
- day = Tuesday
Side note: Doing a search on Yahoo for the word
"Flash" yields this query string:
Here' you can see that the query string is as follows:
This is an example of how the form
data is sent to the search engine via the query
string. You, the user, don't usually care how
the query string works (the query string may even look
like a gibberish). You may not even notice that it is
there in the URL. The CGI program handles the
details for you.
Basic Query String Syntax
The format of the query string is as follows:
variable name and value pair is separated by a '='
an '&' sign separates the variables.
You can have as many variable name and value pairs, but
remember, there is a limit, and I recommend not more than 1024 characters total (including the www... URL part). After
all, if you need more space, you should consider using other
methods, such as reading from a data file.
Several more things that should be noted:
- You can add (type) a query string manually to an URL.
example, I can enter http://www.permadi.com/index.html?message=Hello,
and the page will work as usual. The query string is
simply ignored if the destination URL doesn't do anything with it.
file in the above example does not do anything with the query
string, so it's simply ignored). This is something that doesn't seem
useful, but later you will see how it can be
- Do not put line breaks within a query string. even if
the string is long.
Several things that should be noted about variable names:
- Use only letters, underline, and numbers. Avoid symbols such as '$' or '#'.
- Do not start a name with a number (1message
is an invalid variable name because the name starts with a
number; whereas message1 is a
valid variable name).
Flash will certainly reject
or get confused if you use a
variable name that starts with a number or other special
characters - except underlines (ie: _message, and _1message
are valid names).
- A variable name should not contain any <space>
character (ie: my message is an invalid name,
my_message is a valid name).
And for variable values, there are also rules:
- Characters needs to be URL encoded (see:
URL Encoding). This means
that special characters, such as =, &, <SPACE>,
+ need to be substituted with their URL encoded
format. For example: name=John Doe. Here, the <space>
between John and Doe needs
to be encoded with + sign, so you need to pass it
as name=John+Doe or name=John%20Doe. (Flash doesn't seem to
enforce this, but you should follow the proper way.)
Search for URL encoding on the net for more details on
- If you need to include an & as part
of a value, such as in ingredients=Beef&Pork, then you need to encode the & like
this: ingredients=Beef%26Pork. The %26
is an encoded form of the & sign. The number
26 is the hexadecimal code of the character &. If you
need to know the encoding value of a particular character, consult
an ASCII table.
There are other characters that need to be
encoded, such as <, >, /, ?.
STRING AND FLASH
Now that we know what a query string is, let's see how it applies
When you put a Flash movie on a html page, you will have an
OBJECT tag code that is similar to this:
ID=flaMovie WIDTH=250 HEIGHT=250>
<PARAM NAME=movie VALUE="flaMovie.swf">
<PARAM NAME=quality VALUE=medium>
<PARAM NAME=bgcolor VALUE=#99CC33>
<EMBED src="flaMovie.swf" bgcolor=#99CC33 WIDTH=250 HEIGHT=250
In that example, the Flash movie filename
is: flaMovie.swf. Notice how that filename is used
twice; this is the result of incompatibilities between Netscape
and Internet Explorer. To be on the safe side, you should
You can append a query string following
the Flash movie filename, and Flash will get the variable(s) from
the query string for you automatically. The variable(s)
will go into the _root or _level0 of the movie. Note: ActionScript 3 user should go here after reding this tutorial for Action Script 3 way of accessing query strings.
see some examples on the Next Page.
(C) F. Permadi