PHP: Convert a String to Variable

Question

I've got a multidimensional associative array which includes an elements like

$data["status"]
$data["response"]["url"]
$data["entry"]["0"]["text"]

I've got a strings like:

$string = 'data["status"]';
$string = 'data["response"]["url"]';
$string = 'data["entry"]["0"]["text"]';

How can I convert the strings into a variable to access the proper array element? This method will need to work across any array at any of the dimensions.

Answer 1

You would access them like:

print $$string;

Answer 2

Quick and dirty:

echo eval('return $'. $string . ';');

Of course the input string would need to be be sanitized first.

If you don't like quick and dirty... then this will work too and it doesn't require eval which makes even me cringe.

It does, however, make assumptions about the string format:

<?php
$data['response'] = array(
    'url' => 'http://www.testing.com'
);

function extract_data($string) {
    global $data;

    $found_matches = preg_match_all('/\[\"([a-z]+)\"\]/', $string, $matches);
    if (!$found_matches) {
            return null;
    }

    $current_data = $data;
    foreach ($matches[1] as $name) {
            if (key_exists($name, $current_data)) {
                    $current_data = $current_data[$name];
            } else {
                    return null;
            }
    }

    return $current_data;
} 

echo extract_data('data["response"]["url"]');
?>

Answer 3

PHP's variable variables will help you out here. You can use them by prefixing the variable with another dollar sign:

$foo = "Hello, world!";
$bar = "foo";
echo $$bar; // outputs "Hello, world!"

Answer 4

Found this on the Variable variables page:

function VariableArray($data, $string) { 
    preg_match_all('/\[([^\]]*)\]/', $string, $arr_matches, PREG_PATTERN_ORDER); 

    $return = $arr; 
    foreach($arr_matches[1] as $dimension) { $return = $return[$dimension]; }

    return $return; 
}