Access array element indexed by numerical string

Question

I have encountered something odd.

I have a php array, indexed with numerical keys. However it appears impossible to access any of the elements because php automatically treats numerical strings as integers, causing an illegal offset notice.

Under normal circumstances its imposable to create a php array with numerical string indexes, but it can happen with type casting.

To reproduce:

$object = new stdClass();
$object->{'1'} = 'one';

$array = (array) $object;

var_dump($array);
/* produces
array(1) {
  ["1"]=>
  string(3) "one"
}
*/

//none of the following will work
$key = '1';
echo $array[1], $array['1'], $array["1"], $array[(string)1], $array[$key];

Is this just an edge case bug? I only encountered the problem when attempting to improve my answer for another SO question

Live code example: http://codepad.viper-7.com/dFSlH1

String keys containing valid integer values would be cast to integer keys automatically in “normal” array creation – but it seems casting from object to array doesn’t apply the same logic. It can be fixed however, by using $array = array_combine(array_keys($array), array_values($array)); after your line that creates the array from the object. codepad.viper-7.com/v5rGJa — C3roe
– C3roe, Commented Nov 13, 2015 at 15:34
to add to danjam's comment... with a few notable exceptions: integer properties are unaccessible; — Dale
– Dale, Commented Nov 13, 2015 at 15:34
@danjam Are, well spotted. So it is documented. Though i would still consider it a bug. — Steve
– Steve, Commented Nov 13, 2015 at 15:36

swidmann · Accepted Answer · 2015-11-13 21:22:21Z

Unbelievable but this is normal behavior in php, it was considered as a bug (link) in the year 2008.

But they just pointed out to the manual for the cast with (array):

If an object is converted to an array, the result is an array whose elements are the object's properties. The keys are the member variable names, with a few notable exceptions: integer properties are unaccessible;

You can use get_object_vars() instead:

$object = new stdClass();
$object->{'1'} = 'one';

$array = get_object_vars( $object );

$key = '1';
echo $array[1]."<br>";
echo $array['1']."<br>";
echo $array["1"]."<br>";
echo $array[(string)1]."<br>";
echo $array[$key]."<br>";

Doesn't explain why this happens, but is a solution to avoid the cast problem.

Off topic but I thought maybe it is interesting. Found this in the manual.

To avoid these kind of problems, always use an integer OR a string as index, don't mix it up and don't use integers in a string.

Example of mixed array:

$array = array(
    1    => "a",
    "1"  => "b",//overrides 1
    1.5  => "c",//overrides "1"
    true => "d",//overrides 1.5
);

var_dump($array);

wogsland · Accepted Answer · 2015-11-13 15:34:06Z

5

You can use

$vars  = get_object_vars($object);
echo $vars[1];

answered Nov 13, 2015 at 15:34

wogsland

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1 Comment

swidmann Over a year ago

oh great, you were faster than me :)

C3roe · Accepted Answer · 2015-11-13 15:44:38Z

2

String keys containing valid integer values would be cast to integer keys automatically in “normal” array creation – but it seems casting from object to array doesn’t apply the same logic.

It can be fixed however, by using

$array = array_combine(array_keys($array), array_values($array));

after your line that creates the array from the object. http://codepad.viper-7.com/v5rGJa

Although, same as Dave already said in his comment, using get_object_vars looks like a “cleaner” solution to me as well.

answered Nov 13, 2015 at 15:44

C3roe

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Comments

Harikrishnan · Accepted Answer · 2015-11-13 15:44:52Z

1

foreach ($array as $key => $value){
    var_dump($key);
    var_dump($value);
}

shows

string(1) "1"
string(3) "one"

But echo $array['"1"']; gives

E_NOTICE :  type 8 -- Undefined index: "1" -- at line 8

That's strange!

answered Nov 13, 2015 at 15:44

Harikrishnan

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