ArrayHelper

Additionally to the rich set of PHP array functions, the Yii array helper provides extra static methods allowing you to deal with arrays more efficiently.

Getting Values

Retrieving values from an array, an object or a complex structure consisting of both using standard PHP is quite repetitive. You have to check if key exists with isset first, then if it does you're getting it, if not, providing default value:

class User
{
    public $name = 'Alex';
}

$array = [
    'foo' => [
        'bar' => new User(),
    ]
];

$value = isset($array['foo']['bar']->name) ? $array['foo']['bar']->name : null;

Yii provides a very convenient method to do it:

$value = ArrayHelper::getValue($array, 'foo.bar.name');

First method argument is where we're getting value from. Second argument specifies how to get the data. It could be one of the following:

• Name of array key or object property to retrieve value from.
• Set of dot separated array keys or object property names. The one we've used in the example above.
• A callback returning a value.

The callback should be the following:

$fullName = ArrayHelper::getValue($user, function ($user, $defaultValue) {
    return $user->firstName . ' ' . $user->lastName;
});

Third optional argument is default value which is null if not specified. Could be used as follows:

$username = ArrayHelper::getValue($comment, 'user.username', 'Unknown');

In case you want to get the value and then immediately remove it from array you can use remove method:

$array = ['type' => 'A', 'options' => [1, 2]];
$type = ArrayHelper::remove($array, 'type');

After executing the code $array will contain ['options' => [1, 2]] and $type will be A. Note that unlike getValue method, remove supports simple key names only.

Checking Existence of Keys

ArrayHelper::keyExists works the same way as array_key_exists except that it also supports case-insensitive key comparison. For example,

$data1 = [
    'userName' => 'Alex',
];

$data2 = [
    'username' => 'Carsten',
];

if (!ArrayHelper::keyExists('username', $data1, false) || !ArrayHelper::keyExists('username', $data2, false)) {
    echo "Please provide username.";
}

Retrieving Columns

Often you need to get a column of values from array of data rows or objects. Common example is getting a list of IDs.

$array = [
    ['id' => '123', 'data' => 'abc'],
    ['id' => '345', 'data' => 'def'],
];
$ids = ArrayHelper::getColumn($array, 'id');

The result will be ['123', '345'].

If additional transformations are required or the way of getting value is complex, second argument could be specified as an anonymous function:

$result = ArrayHelper::getColumn($array, function ($element) {
    return $element['id'];
});

Re-indexing Arrays

In order to index an array according to a specified key, the index method can be used. The input should be either multidimensional array or an array of objects. The $key can be either a key name of the sub-array, a property name of object, or an anonymous function that must return the value that will be used as a key.

The $groups attribute is an array of keys, that will be used to group the input array into one or more sub-arrays based on keys specified.

If the $key attribute or its value for the particular element is null and $groups is not defined, the array element will be discarded. Otherwise, if $groups is specified, array element will be added to the result array without any key.

For example:

$array = [
    ['id' => '123', 'data' => 'abc', 'device' => 'laptop'],
    ['id' => '345', 'data' => 'def', 'device' => 'tablet'],
    ['id' => '345', 'data' => 'hgi', 'device' => 'smartphone'],
];
$result = ArrayHelper::index($array, 'id');

The result will be an associative array, where the key is the value of id attribute:

[
    '123' => ['id' => '123', 'data' => 'abc', 'device' => 'laptop'],
    '345' => ['id' => '345', 'data' => 'hgi', 'device' => 'smartphone']
    // The second element of an original array is overwritten by the last element because of the same id
]

Anonymous function, passed as a $key, gives the same result:

$result = ArrayHelper::index($array, function ($element) {
    return $element['id'];
});

Passing id as a third argument will group $array by id:

$result = ArrayHelper::index($array, null, 'id');

The result will be a multidimensional array grouped by id on the first level and not indexed on the second level:

[
    '123' => [
        ['id' => '123', 'data' => 'abc', 'device' => 'laptop']
    ],
    '345' => [ // all elements with this index are present in the result array
        ['id' => '345', 'data' => 'def', 'device' => 'tablet'],
        ['id' => '345', 'data' => 'hgi', 'device' => 'smartphone'],
    ]
]

An anonymous function can be used in the grouping array as well:

$result = ArrayHelper::index($array, 'data', [function ($element) {
    return $element['id'];
}, 'device']);

The result will be a multidimensional array grouped by id on the first level, by device on the second level and indexed by data on the third level:

[
    '123' => [
        'laptop' => [
            'abc' => ['id' => '123', 'data' => 'abc', 'device' => 'laptop']
        ]
    ],
    '345' => [
        'tablet' => [
            'def' => ['id' => '345', 'data' => 'def', 'device' => 'tablet']
        ],
        'smartphone' => [
            'hgi' => ['id' => '345', 'data' => 'hgi', 'device' => 'smartphone']
        ]
    ]
]

Building Maps

In order to build a map (key-value pairs) from a multidimensional array or an array of objects you can use map method. The $from and $to parameters specify the key names or property names to set up the map. Optionally, one can further group the map according to a grouping field $group. For example,

$array = [
    ['id' => '123', 'name' => 'aaa', 'class' => 'x'],
    ['id' => '124', 'name' => 'bbb', 'class' => 'x'],
    ['id' => '345', 'name' => 'ccc', 'class' => 'y'],
];

$result = ArrayHelper::map($array, 'id', 'name');
// the result is:
// [
//     '123' => 'aaa',
//     '124' => 'bbb',
//     '345' => 'ccc',
// ]

$result = ArrayHelper::map($array, 'id', 'name', 'class');
// the result is:
// [
//     'x' => [
//         '123' => 'aaa',
//         '124' => 'bbb',
//     ],
//     'y' => [
//         '345' => 'ccc',
//     ],
// ]

Multidimensional Sorting

multisort method helps to sort an array of objects or nested arrays by one or several keys. For example,

$data = [
    ['age' => 30, 'name' => 'Alexander'],
    ['age' => 30, 'name' => 'Brian'],
    ['age' => 19, 'name' => 'Barney'],
];
ArrayHelper::multisort($data, ['age', 'name'], [SORT_ASC, SORT_DESC]);

After sorting we'll get the following in $data:

[
    ['age' => 19, 'name' => 'Barney'],
    ['age' => 30, 'name' => 'Brian'],
    ['age' => 30, 'name' => 'Alexander'],
];

Second argument that specifies keys to sort by can be a string if it's a single key, an array in case of multiple keys or an anonymous function like the following one:

ArrayHelper::multisort($data, function($item) {
    return isset($item['age']) ? ['age', 'name'] : 'name';
});

Third argument is direction. In case of sorting by a single key it could be either SORT_ASC or SORT_DESC. If sorting by multiple values you can sort each value differently by providing an array of sort direction.

Last argument is PHP sort flag that could take the same values as the ones passed to PHP sort().

Detecting Array Types

It is handy to know whether an array is indexed or an associative. Here's an example:

// no keys specified
$indexed = ['Qiang', 'Paul'];
echo ArrayHelper::isIndexed($indexed);

// all keys are strings
$associative = ['framework' => 'Yii', 'version' => '2.0'];
echo ArrayHelper::isAssociative($associative);

HTML Encoding and Decoding Values

In order to encode or decode special characters in an array of strings into HTML entities you can use the following:

$encoded = ArrayHelper::htmlEncode($data);
$decoded = ArrayHelper::htmlDecode($data);

Only values will be encoded by default. By passing second argument as false you can encode array's keys as well. Encoding will use application charset and could be changed via third argument.

Merging Arrays

You can use ArrayHelper::merge() to merge two or more arrays into one recursively. If each array has an element with the same string key value, the latter will overwrite the former (different from array_merge_recursive()). Recursive merging will be conducted if both arrays have an element of array type and are having the same key. For integer-keyed elements, the elements from the latter array will be appended to the former array. You can use yii\helpers\UnsetArrayValue object to unset value from previous array or yii\helpers\ReplaceArrayValue to force replace former value instead of recursive merging.

For example:

$array1 = [
    'name' => 'Yii',
    'version' => '1.1',
    'ids' => [
        1,
    ],
    'validDomains' => [
        'example.com',
        'www.example.com',
    ],
    'emails' => [
        'admin' => '[email protected]',
        'dev' => '[email protected]',
    ],
];

$array2 = [
    'version' => '2.0',
    'ids' => [
        2,
    ],
    'validDomains' => new \yii\helpers\ReplaceArrayValue([
        'yiiframework.com',
        'www.yiiframework.com',
    ]),
    'emails' => [
        'dev' => new \yii\helpers\UnsetArrayValue(),
    ],
];

$result = ArrayHelper::merge($array1, $array2);

The result will be:

[
    'name' => 'Yii',
    'version' => '2.0',
    'ids' => [
        1,
        2,
    ],
    'validDomains' => [
        'yiiframework.com',
        'www.yiiframework.com',
    ],
    'emails' => [
        'admin' => '[email protected]',
    ],
]

Converting Objects to Arrays

Often you need to convert an object or an array of objects into an array. The most common case is converting active record models in order to serve data arrays via REST API or use it otherwise. The following code could be used to do it:

$posts = Post::find()->limit(10)->all();
$data = ArrayHelper::toArray($posts, [
    'app\models\Post' => [
        'id',
        'title',
        // the key name in array result => property name
        'createTime' => 'created_at',
        // the key name in array result => anonymous function
        'length' => function ($post) {
            return strlen($post->content);
        },
    ],
]);

The first argument contains the data we want to convert. In our case we're converting a Post AR model.

The second argument is conversion mapping per class. We're setting a mapping for Post model. Each mapping array contains a set of mappings. Each mapping could be:

• A field name to include as is.
• A key-value pair of desired array key name and model column name to take value from.
• A key-value pair of desired array key name and a callback which returns value.

The result of conversion above for single model will be:

[
    'id' => 123,
    'title' => 'test',
    'createTime' => '2013-01-01 12:00AM',
    'length' => 301,
]

It is possible to provide default way of converting object to array for a specific class by implementing Arrayable interface in that class.

Testing against Arrays

Often you need to check if an element is in an array or a set of elements is a subset of another. While PHP offers in_array(), this does not support subsets or \Traversable objects.

To aid these kinds of tests, yii\helpers\ArrayHelper provides isIn() and isSubset() with the same signature as in_array().

// true
ArrayHelper::isIn('a', ['a']);
// true
ArrayHelper::isIn('a', new ArrayObject(['a']));

// true 
ArrayHelper::isSubset(new ArrayObject(['a', 'c']), new ArrayObject(['a', 'b', 'c']));