Difference Between $_GET and $_POST in PHP

This article explains the primary differences between the $_GET and $_POST superglobal variables in PHP. It covers how they transmit data, their security implications, storage limits, and the specific scenarios where you should use one over the other.

The Core Difference

The fundamental difference between $_GET and $_POST lies in how they send data to the server.

$_GET sends data by appending it to the URL as query parameters.
$_POST sends data invisibly within the body of the HTTP request.

Detailed Comparison

To choose the right method for your PHP application, you must understand how they differ across several key areas:

1. Security

$_GET is insecure for sensitive data. Because the data is appended to the URL, it is visible in the browser address bar. It also gets stored in the browser’s history, web server logs, and can be cached by proxy servers. Never use $_GET for passwords, credit card numbers, or other sensitive information.
$_POST is more secure. Data is sent within the HTTP request body, meaning it is not visible in the URL or stored in browser history. However, for absolute security, you must still use HTTPS to encrypt the transit of $_POST data.

2. Data Limits

$_GET has strict limits. Since URLs have length restrictions imposed by browsers and web servers (usually around 2,048 characters), $_GET is unsuitable for sending large amounts of data.
$_POST has no theoretical limit. It can be used to send large amounts of data, including file uploads and multi-part form submissions. The only limits are those configured in your server’s php.ini file (such as post_max_size and upload_max_filesize).

3. Bookmarking and Caching

$_GET requests can be bookmarked and cached. Since all variables are part of the URL, users can bookmark a specific query result or share the link with others.
$_POST requests cannot be bookmarked. If a user attempts to bookmark a page generated by a $_POST submission, the bookmark will only save the URL, not the submitted data. Reloading a $_POST page will also trigger a browser warning asking the user to resubmit the form.

Quick Reference Summary

Feature	`$_GET`	`$_POST`
Data Location	URL Query String	HTTP Request Body
Visibility	Public (visible in URL)	Hidden from URL
Max Capacity	~2,048 characters	No limit (configurable)
Security	Low (unsuitable for sensitive data)	Medium (suitable for sensitive data with HTTPS)
Can be Bookmarked?	Yes	No
Can be Cached?	Yes	No

When to Use Which?

Use `$_GET` when:

The submission is a simple query that retrieves data from the database without modifying it (idempotent actions).
You want the user to be able to bookmark, share, or refresh the page results (e.g., search engines, product filters, category pages).

Use `$_POST` when:

The submission modifies data on the server (e.g., creating a new user account, updating a database, or deleting a record).
You are transmitting sensitive information like passwords, API keys, or personal details.
You are uploading files (images, documents) or sending large blocks of text.