What is the best way to access unknown array elements without generating PHP notice?

Question

If I have this array,

ini_set('display_errors', true);
error_reporting(E_ALL);

$arr = array(
  'id' => 1234,
  'name' => 'Jack',
  'email' => '[email protected]',
  'city' => array(
    'id' => 55,
    'name' => 'Los Angeles',
    'country' => array(
      'id' => 77,
      'name' => 'USA',
     ),
  ),
);

I can get the country name with

$name = $arr['city']['country']['name'];

But if the country array doesn't exist, PHP will generate warning:

Notice: Undefined index ... on line xxx

Sure I can do the test first:

if (isset($arr['city']['country']['name'])) {
  $name = $arr['city']['country']['name'];
} else {
  $name = '';  // or set to default value;
}

But that is inefficient. What is the best way to get $arr['city']['country']['name'] without generating PHP Notice if it doesn't exist?

Where does the data come from? If from a third party, you should write one parse function to parse this into a standardized data structure of which you know which keys exist and which don't... — deceze
– deceze ♦, Commented May 28, 2012 at 8:32
@deceze: It is inefficient since getting a single value takes 4+ lines. — flowfree
– flowfree, Commented May 28, 2012 at 8:33

flowfree · Accepted Answer · 2012-05-28 09:07:23Z

5

I borrowed the code below from Kohana. It will return the element of multidimensional array or NULL (or any default value chosen) if the key doesn't exist.

function _arr($arr, $path, $default = NULL) 
{
  if (!is_array($arr))
    return $default;

  $cursor = $arr;
  $keys = explode('.', $path);

  foreach ($keys as $key) {
    if (isset($cursor[$key])) {
      $cursor = $cursor[$key];
    } else {
      return $default;
    }
  }

  return $cursor;
}

Given the input array above, access its elements with:

echo _arr($arr, 'id');                    // 1234
echo _arr($arr, 'city.country.name');     // USA
echo _arr($arr, 'city.name');             // Los Angeles
echo _arr($arr, 'city.zip', 'not set');   // not set

edited May 28, 2012 at 9:07

answered May 28, 2012 at 8:26

flowfree

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Comments

Core Xii · Accepted Answer · 2012-05-28 09:12:17Z

3

The @ error control operator suppresses any errors generated by an expression, including invalid array keys.

$name = @$arr['city']['country']['name'];

answered May 28, 2012 at 9:12

Core Xii

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2 Comments

flowfree Over a year ago

Actually I want to write clean code, so I avoid @ to catch any warnings and notices and fix them.

Core Xii Over a year ago

If you wanted to write clean code, then you would use isset() as you explain in your very question. But it's verbose, which is why you're looking for alternatives. @ is the least verbose of them.

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