PHP - $_POST

$_POST is a superglobal variable that holds an associative array of values submitted through an HTML form using the POST method. Here's a breakdown of its key aspects:

• HTML forms

• JavaScript HTTP requests

• $_POST in HTML Forms

$_POST is a superglobal variable in PHP that allows you to access data submitted by a form using the POST method. .

To demonstrate this, we start by creating a simple HTML form:

HTML form

<html>
<body>

<form method="POST" action="demo_request.php">
  Name: <input type="text" name="fname">
  <input type="submit">
</form>

</body>
</html>

When a user clicks the submit button, the form data is sent to a PHP file specified in the action attribute of the <form> tag.

In the action file we can use the $_POST variable to collect the value of the input field.

PHP file

$name = $_POST['fname'];
echo $name;

In the example below we have put the HTML form and PHP code in the same PHP file.

We have also added some extra lines for security.

HTML form

<!DOCTYPE html>
<html>
<body>

<form method="post" action="/tutorials/php/php-post.php">
  Name: <input type="text" name="fname">
  <input type="submit">
</form>

<?php
if ($_SERVER["REQUEST_METHOD"] == "POST") {
    // collect value of input field
    $name = $_POST['fname'];
    if (empty($name)) {
        echo "Name is empty";
    } else {
        echo $name;
    }
}
?>

</body>
</html>

Output

Name:"--------"submit

• $_POST in JavaScript HTTP Requests

When sending a HTTP request in JavaScript, you can specify that the HTTP method is POST.

To demonstrate this we start by creating a JavaScript function containing a HTTP request:

JavaScript function


function myfunction() {
  const xhttp = new XMLHttpRequest();
  xhttp.open("POST", "demo_phpfile.php");
  xhttp.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
  xhttp.onload = function() {
    document.getElementById("demo").innerHTML = this.responseText;
  }
  xhttp.send("fname=Mary");
  }
}

The code above will:

Intiate a HTTP request
Set the HTTP method to POST
Set a valid request header
Create a function to execute when the request is done
Send the HTTP request with a variable fname set to Mary