Differences between Simple Variables and Variable Variables

Home > PHP > General

Q

What is the difference between $message and $$message in PHP?

✍: FYIcenter

A

$message is a simple variable with a fixed name which is called "message".

$$message is a variable variable with a variable name which is stored in another variable called $message.

If $message contains "user", $$message is the same as $user. For example, this code will produce "bob" and "bob":

<?php
$holder = 'user';
$$holder = 'bob';
echo $$holder;
echo $user;
?>

2007-02-27, 6137👍, 0💬

Number of Days between Two Dates
How can we know the number of days between two given dates in PHP? Simple arithmetic: <?php $date1 = date('Y-m-d'); $date2 = '2006-07-01'; $days = (strtotime($date1) - strtotime($date2)) / (60 * 60 * 24); $days = (int) $days; echo "Number of days since '2006-07-01': $days"; ?> 2007-02-27, 7325👍, 0💬

Persistent Cookies
What Is a Persistent Cookie? A persistent cookie is a cookie which is stored in a cookie file permanently on the browser's computer. By default, cookies are created as temporary cookies which stored only in the browser's memory. When the browser is closed, temporary cookies will be erased. You shoul... 2007-02-27, 6532👍, 0💬

define() - Defining Constants
How do you define a constant in PHP? You can define a constant by using the define() function. Once a constant is defined, it can never be changed or undefined. For example: <?php define("CONSTANT", "Hello world."); echo CONSTANT; // outputs "Hello world." echo Constant; // outputs "Constant"... 2007-02-27, 6293👍, 0💬

What Is a Session
What Is a Session? A session is a logical object created by the PHP engine to allow you to preserve data across subsequent HTTP requests. There is only one session object available to your PHP scripts at any time. Data saved to the session by a script can be retrieved by the same script or another s... 2007-02-27, 6284👍, 0💬

What is PHP
What is PHP? The PHP Hypertext Preprocessor is a programming language that allows web developers to create dynamic content that interacts with databases. PHP is basically used for developing web based software applications. 2007-02-27, 6283👍, 0💬

require(), include() and include_once() Functions
What are the differences between require(), include() and include_once() functions in PHP? All three functions are used to include and evaluate a file into the current script execution. The include_once() statement includes and evaluates the specified file during the execution of the script. This is... 2007-02-27, 6251👍, 0💬

Differences between Simple Variables and Variable Variables
What is the difference between $message and $$message in PHP? $message is a simple variable with a fixed name which is called "message". $$message is a variable variable with a variable name which is stored in another variable called $message. If $message contains "user", $$message is the same as $u... 2007-02-27, 6138👍, 0💬

What Is PEAR
What Is PEAR? PEAR is the next revolution in PHP. This repository is bringing higher level programming to PHP. PEAR is a framework and distribution system for reusable PHP components. It eases installation by bringing an automated wizard, and packing the strength and experience of PHP users into a n... 2007-02-27, 6104👍, 0💬

Uploading Files with File Input Fields in a Form
How To Write the FORM Tag Correctly for Uploading Files? When users clicks the submit button, files specified in the <INPUT TYPE=FILE...> will be transferred from the browser to the Web server. This transferring (uploading) process is controlled by a properly written <FORM...> tag as: ... 2007-02-27, 6094👍, 0💬

All rights in the contents of this web site are reserved by the individual author. fyicenter.com does not guarantee the truthfulness, accuracy, or reliability of any contents.