In PHP there are two ways to send information to server.
These are GET and POST. $_GET and $_POST both are super global variable.
The variable which is always accessible is called as super global variable.
$_GET :
Through URL
<!DOCTYPE html>
<html>
<body>
<a href=“http://www.example.com/action.php?name=john&age=24">Send</a>
</body>
</html>
<!DOCTYPE html>
<html>
<body>
<form action="action_page.php" method="get">
First name:<br>
<input type="text" name="firstname">
<br>
Last name:<br>
<input type="text" name="lastname">
<br><br>
<input type="submit" value="Submit">
</form>
</body>
</html>
In action_page.php we gather the information using $_GET super global variable.
$_POST
<!DOCTYPE html>
<html>
<body>
<form action="action_page.php" method="post">
First name:<br>
<input type="text" name="firstname">
<br>
Last name:<br>
<input type="text" name="lastname">
<br><br>
<input type="submit" value="Submit">
</form>
</body>
</html>
In action_page.php we gather the information using $_POST super global variable.