Variable variables

Constants
November 13, 2018
Operators
November 13, 2018

Sometimes it is convenient to be able to have variable variable names. That is, a variable name which can be set and used dynamically. A normal variable is set with a statement such as:

<?php
$a = 'hello';
?>

A variable variable takes the value of a variable and treats that as the name of a variable. In the above example,hello, can be used as the name of a variable by using two dollar signs. i.e.

<?php
$$a = 'world';
?>

At this point two variables have been defined and stored in the PHP symbol tree: $a with contents “hello” and$hello with contents “world”. Therefore, this statement:

<?php
echo "$a ${$a}";
?>

produces the exact same output as:

<?php
echo "$a $hello";
?>

i.e. they both produce: hello world.

In order to use variable variables with arrays, you have to resolve an ambiguity problem. That is, if you write$$a[1] then the parser needs to know if you meant to use $a[1] as a variable, or if you wanted $$a as the variable and then the [1] index from that variable. The syntax for resolving this ambiguity is: ${$a[1]} for the first case and ${$a}[1] for the second.

Class properties may also be accessed using variable property names. The variable property name will be resolved within the scope from which the call is made. For instance, if you have an expression such as$foo->$bar, then the local scope will be examined for $bar and its value will be used as the name of the property of $foo. This is also true if $bar is an array access.

Sondiva Technologies
Sondiva Technologies
Sondiva Technologies started in 2011 with a vision of providing Quality based Web Hosting and Web Designing Services in Ghaziabad, Delhi NCR. Backed up by full stack developers and designers , with over 500+ Web Projects. They work on opensource Platforms like Wordpress, Magneto, Prestashop, Opencart and Core PHP. Other services are : Responsive Web Designing Domain Registration Services Dedicated & SSD Hosting Virtual Private Servers Google GSuite Mail Servers E-Commerce Shopping Portal Development Web Designing & Application Courses SEO & Digital Marketing

Leave a Reply

Your email address will not be published. Required fields are marked *

Shop Now