Dynamic access to a PHP array

Question

I tried to access with $this->$arrDataName[$key] on the element with the key $key from the array $this->$arrDataName. But PHP interpretes that wrong.

I tried it with { } around the $arrDataName to $this->{$arrDataName}[$key], but it doesn't work.

On php.net I found an advice, but I can't realize it.

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.

Perhaps anyone can help me.

Thanks!

EDIT:

I think it doesn't work, but I forgot to fill the array.
Finally it works. :)
This is the solution: $this->{$arrDataName}[$key]

Macmade · Accepted Answer · 2010-07-13 09:15:34Z

6

Your syntax is correct:

$this->{$varName}[$key]

You can also use an extra variable for this:

$myTempArr = $this->$arrDataName;

$myTempArr[ $key ];

IMHO, readability is better that way...

edited Jul 13, 2010 at 9:15

answered Jul 13, 2010 at 9:09

Macmade

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2 Comments

CSchulz Over a year ago

Thanks for the advice. I know that way, but I search for the one line solution. ;)

CSchulz Over a year ago

I found my problem. The specified array was empty. -.-

NikiC · Accepted Answer · 2010-07-13 09:18:41Z

2

<?php
    class Foo {
        public function __construct() {
            $this->myArray = array('FooBar');
            $arrayName = 'myArray';
            echo $this->{$arrayName}[0];
        }
    }
    new Foo;

This worked perfectly for me, it printed FooBar.

answered Jul 13, 2010 at 9:18

NikiC

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Comments

Bogdan Constantinescu · Accepted Answer · 2010-07-13 09:14:51Z

0

Let's assume your array is $this->arrDataName. You have a $key, so your object would be $this->arrDataName[$key].

If you want the contents of the variable which name is stored in $this->arrDataName[$key] you should do this:

<?php
    echo ${$this->arrDataName[$key]};
?>

answered Jul 13, 2010 at 9:14

Bogdan Constantinescu

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1 Comment

CSchulz Over a year ago

Sorry, but I can't figure out, how that will help me.

Tomasz Struczyński · Accepted Answer · 2010-07-13 09:18:23Z

0

Well, as far as I know, it works. Here how I tested it:

<?php
class tis
{
    var $a = array('a', 'b', 'c');
    var $b = array('x', 'y', 'z');

    public function read($var)
    {
        echo $this->{$var}[1].'<br />';
    }
}

$t = new tis();
$t->read('a');
$t->read('b');
?>

And the output:

b
y

Check correctness of $arrDataName. Turn on debuging and displaying PHP erros (including notices). Maybe you're trying to read non-existing property?

Also, which PHP version you use? I assume PHP5?

answered Jul 13, 2010 at 9:18

Tomasz Struczyński

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3 Comments

Tomasz Struczyński Over a year ago

...and a comment - if possible, it's better not to use this magic. Later on, you'll have problems understanding what you wanted to do. Believe me :)

NikiC Over a year ago

@H3llGhost: You have set error_reporting to E_ALL | E_STRICT? And display_errors is enabled?

CSchulz Over a year ago

Yes. The typical options for developing. ;) I had a board in front of my head.

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