| PHP Manual |
| Prev |
Chapter 7. Variables |
Next |
When a form is submitted to a PHP script, any variables from that form will be
automatically made available to the script by PHP. If the track_vars configuration option is turned on, then these
variables will be located in the associative arrays $HTTP_POST_VARS,
$HTTP_GET_VARS, and/or $HTTP_POST_FILES, according to the source of the variable in
question.
For more information on these variables, please read Predefined variables.
|
Example 7-1. Simple form variable
<form action="foo.php" method="post">
Name: <input type="text" name="username"><br>
<input type="submit">
</form>
|
|
When the above form is submitted, the value from the text input will be available in
$HTTP_POST_VARS['username']. If the
register_globals configuration directive is turned on, then the variable will also be available
as $username in the global scope.
Note: The magic_quotes_gpc
configuration directive affects Get, Post and Cookie values. If turned on, value (It's "PHP!") will
automagically become (It\'s \"PHP!\"). Escaping is needed for DB insertion. Also see addslashes(),
stripslashes() and
magic_quotes_sybase.
PHP also understands arrays in the context of form variables (see the related faq). You may, for example, group related variables together, or use
this feature to retrieve values from a multiple select input:
|
Example 7-2. More complex form variables
<form action="array.php" method="post">
Name: <input type="text" name="personal[name]"><br>
Email: <input type="text" name="personal[email]"><br>
Beer: <br>
<select multiple name="beer[]">
<option value="warthog">Warthog
<option value="guinness">Guinness
<option value="stuttgarter">Stuttgarter Schwabenbr∓auml;u
</select>
<input type="submit">
</form>
|
|
In PHP 3, the array form variable usage is limited to single-dimensional arrays. In PHP 4,
no such restriction applies.
When submitting a form, it is possible to use an image instead of the standard submit
button with a tag like:
<input type="image" src="image.gif" name="sub">
|
When the user clicks somewhere on the image, the accompanying form will be transmitted to
the server with two additional variables, sub_x and sub_y. These contain the coordinates of the
user click within the image. The experienced may note that the actual variable names sent by the
browser contains a period rather than an underscore, but PHP converts the period to an underscore
automatically.
PHP transparently supports HTTP cookies as defined by Netscape's Spec. Cookies
are a mechanism for storing data in the remote browser and thus tracking or identifying return
users. You can set cookies using the setcookie()
function. Cookies are part of the HTTP header, so the SetCookie function must be called before any
output is sent to the browser. This is the same restriction as for the header() function. Any cookies sent to you from the client will
automatically be turned into a PHP variable just like GET and POST method data.
If you wish to assign multiple values to a single cookie, just add [] to the
cookie name. For example:
setcookie("MyCookie[]", "Testing", time()+3600);
|
Note that a cookie will replace a previous cookie by the same name in your browser
unless the path or domain is different. So, for a shopping cart application you may want to keep a
counter and pass this along. i.e.
|
Example 7-3. SetCookie Example
$Count++;
setcookie("Count", $Count, time()+3600);
setcookie("Cart[$Count]", $item, time()+3600);
|
|
PHP automatically makes environment variables available as normal PHP
variables.
echo $HOME; /* Shows the HOME environment variable, if set. */
|
Since information coming in via GET, POST and Cookie mechanisms also automatically
create PHP variables, it is sometimes best to explicitly read a variable from the environment in
order to make sure that you are getting the right version. The
getenv() function can be used for this. You can also set an environment variable with the
putenv() function.
Typically, PHP does not alter the names of variables when they are passed into a
script. However, it should be noted that the dot (period, full stop) is not a valid character in a
PHP variable name. For the reason, look at it:
$varname.ext; /* invalid variable name */
|
Now, what the parser sees is a variable named $varname, followed by the string
concatenation operator, followed by the barestring (i.e. unquoted string which doesn't match any
known key or reserved words) 'ext'. Obviously, this doesn't have the intended result.
For this reason, it is important to note that PHP will automatically replace any
dots in incoming variable names with underscores.
Because PHP determines the types of variables and converts them (generally) as
needed, it is not always obvious what type a given variable is at any one time. PHP includes
several functions which find out what type a variable is. They are
gettype(), is_long(), is_double(),
is_string(), is_array(), and is_object().
|
