Easy if you know how?

stubarny

Hi everyone,

How do I create a variable name made of other variable names and then query it?

i.e. what do i have to replace "${$car}" with in the code below to make it work?

$car = ford;
$ford = good;

if ( ${$car} == 'good' ) # This line doesn't work!
{
echo "it works!";
}

Thanks for your help!

Stu

NogDog

It works for me (though it would probably be better if you quoted the string literals you are assigning to each variable). Both of these worked for me:

<?php
$car = 'ford';
$ford = 'good';
if ( ${$car} == 'good' ) # This line doesn't work!
{
   echo "it works!";
}
?>

<?php
$car = 'ford';
$ford = 'good';
if ( $$car == 'good' ) # This line doesn't work!
{
   echo "it works!";
}
?>

scrupul0us

very strange concept... what practical application would this have?

Shrike

A (pointless) reimplementation of extract().

$arr = array( 'foo' => 1, 'bar' => 2 );
foreach( $arr as $key => $value )
{
	$$key = $value;
}
echo $foo;
echo $bar;

🙂

greenie2600

These are known as variable variables. The braces are only necessary if you're using complex expressions; otherwise, a double $ works fine.

They're also evil. One of the apps I maintain uses them extensively on certain pages, and they wreak havoc on your variable scope. There's really no sensible reason to use them; by including them in PHP, the dev team is just giving you more bullets with which to shoot yourself in the foot. PHP's "everything-plus-the-kitchen-sink" approach is a godsend at some times (as you'll realize if you ever need to calculate the date of Easter for a given yearthe first Sunday after the first full moon which falls on or after the vernal equinox), and a curse at others.