PHP Manual: Variables From External Sources

HTML Forms (GET and POST)

When a form is submitted to a PHP script, the information from that form is automatically made available to the script. There are few ways to access this information, for example:

Example #1 A simple HTML form

<form action="foo.php" method="post">
    Name:  <input type="text" name="username" /><br />
    Email: <input type="text" name="email" /><br />
    <input type="submit" name="submit" value="Submit me!" />
</form>

As of PHP 5.4.0, there are only two ways to access data from your HTML forms. Currently available methods are listed below:

Example #2 Accessing data from a simple POST HTML form


<?php
echo $_POST['username'];
echo $_REQUEST['username'];
?>

There were some other ways of accessing user input in old PHP versions. These are listed below. See changelog at the bottom of the page for more details.

Example #3 Old methods of accessing user input


<?php
// WATCH OUT: these methods ARE NOT supported anymore.
// Valid ones were described above.

// Using import_request_variables() - this function has been removed in PHP 5.4.0
   import_request_variables('p', 'p_');
   echo $p_username;

// These long predefined variables were removed in PHP 5.4.0
   echo $HTTP_POST_VARS['username'];

// Using register_globals. This feature was removed in PHP 5.4.0
   echo $username;
?>

Using a GET form is similar except you'll use the appropriate GET predefined variable instead. GET also applies to the QUERY_STRING (the information after the '?' in a URL). So, for example, http://www.example.com/test.php?id=3 contains GET data which is accessible with $_GET['id']. See also $_REQUEST.

Note:
Dots and spaces in variable names are converted to underscores. For example <input name="a.b" /> becomes $_REQUEST["a_b"].

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. For example, let's post a form to itself and upon submission display the data:

Example #4 More complex form variables


<?php
if ($_POST) {
    echo '<pre>';
    echo htmlspecialchars(print_r($_POST, true));
    echo '</pre>';
}
?>
<form action="" 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>
        <option value="guinness">Guinness</option>
        <option value="stuttgarter">Stuttgarter Schwabenbräu</option>
    </select><br />
    <input type="submit" value="submit me!" />
</form>

IMAGE SUBMIT variable names

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.

HTTP Cookies

PHP transparently supports HTTP cookies as defined by » RFC 6265. 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. Cookie data is then available in the appropriate cookie data arrays, such as $_COOKIE as well as in $_REQUEST. See the setcookie manual page for more details and examples.

If you wish to assign multiple values to a single cookie variable, you may assign it as an array. For example:


<?php
  setcookie("MyCookie[foo]", 'Testing 1', time()+3600);
  setcookie("MyCookie[bar]", 'Testing 2', time()+3600);
?>

That will create two separate cookies although MyCookie will now be a single array in your script. If you want to set just one cookie with multiple values, consider using serialize or explode on the value first.

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 #5 A setcookie example


<?php
if (isset($_COOKIE['count'])) {
    $count = $_COOKIE['count'] + 1;
} else {
    $count = 1;
}
setcookie('count', $count, time()+3600);
setcookie("Cart[$count]", $item, time()+3600);
?>

Dots in incoming variable names

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:


<?php
$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.

Determining variable types

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, such as: gettype, is_array, is_float, is_int, is_object, and is_string. See also the chapter on Types.

Changelog

Version	Description
5.4.0	Register Globals, Magic Quotes and register_long_arrays has been removed
5.3.0	Register Globals, Magic Quotes and register_long_arrays became deprecated
4.2.0	register_globals directive defaults to off.
4.1.0	Superglobal arrays, like `$_POST` and `$_GET` became available