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
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
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.
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
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.
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:
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.
HTTP being a text protocol, most, if not all, content that comes in Superglobal arrays, like $_POST and $_GET will remain as strings. PHP will not try to convert values to a specific type. In the example below, $_GET["var1"] will contain the string "null" and $_GET["var2"], the string "123".