将字符串转换为变量

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

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 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

This can be done in a much simpler way. All you have to do is think about what function PHP provides that creates variables.

$string = 'myvariable';
extract(array($string => $string));
echo $myvariable;

done!

Answer 4

You can pass by reference with the operator & . So in your example you'll have something like this

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

Otherwise you need to do something like this:

$titular = array();
for ($r = 1; $r < $rooms + 1; $r ++)
{
    $title = "titular_title_$r";
    $firstName = "titular_firstName_$r";
    $lastName = "titular_lastName_$r";
    $phone = "titular_phone_$r";
    $email = "titular_email_$r";
    $bedType = "bedType_$r";
    $smoker = "smoker_$r";

    $titular[] = array(
        "title" => $$title,
        "first_name" => $$firstName,
        "last_name" => $$lastName,
        "phone" => $$phone,
        "email" => $$email,
        "bedType" => $$bedType,
        "smoker" => $$smoker
    );
}

Answer 5

There are native PHP function for this: use http://php.net/manual/ru/function.parse-str.php (parse_str()).

don't forget to clean up the string from '"' before parsing.

Answer 6

您可以访问它们，如：

print $$string;

Answer 7

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; 
} 

Answer 8

Perhaps this option is also suitable:

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

function getIn($arr, $params)
{
    if(!is_array($arr)) {
        return null;
    }
    if (array_key_exists($params[0], $arr) && count($params) > 1) {
        $bf = $params[0];
        array_shift($params);
        return getIn($arr[$bf], $params);
    } elseif (array_key_exists($params[0], $arr) && count($params) == 1) {

        return $arr[$params[0]];
    } else {
        return null;
}
}

preg_match_all('/(?:(\w{1,}|\d))/', $string, $arr_matches, PREG_PATTERN_ORDER);

array_shift($arr_matches[0]);
print_r(getIn($data, $arr_matches[0]));

Ps it's work for me.

Answer 9

I was struggling with that as well, I had this :

$user  =  array('a'=>'alber', 'b'=>'brad'...);

$array_name = 'user';

and I was wondering how to get into albert.

at first I tried

$value_for_a = $$array_name['a']; // this dosen't work 

then

eval('return $'.$array_name['a'].';'); // this dosen't work, maybe the hoster block eval which is very common

then finally I tried the stupid thing:

$array_temp=$$array_name;
$value_for_a = $array_temp['a'];

and this just worked Perfect! wisdom, do it simple do it stupid.

I hope this answers your question

Answer 10

You can also use curly braces (complex variable notation) to do some tricks:

$h = 'Happy';
$n = 'New';
$y = 'Year';
$wish = ${$h.$n.$y};
echo $wish;