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    array_udiff

    (PHP 5, PHP 7, PHP 8)

    array_udiff — 用回调函数比较数据来计算数组的差集

    说明

    array_udiff(array $array, array ...$arrays, callable $value_compare_func): array

    使用回调函数比较数据，计算数组的不同之处。和 array_diff() 不同的是，前者使用内置函数进行数据比较。

    参数

    array

    第一个数组。

    arrays

    要对比的数组。

    value_compare_func

    在第一个参数小于，等于或大于第二个参数时，该比较函数必须相应地返回一个小于，等于或大于 0 的整数。

    callback(mixed $a, mixed $b): int
    警告

    从比较函数中返回非整数值，例如 float，将导致内部强制转换为 callback 返回值为 int。因此，诸如 0.99 和 0.1 之类的值都将被转换为整数值 0，将这些值比较的话将会是相等。

    警告

    排序回调必须以任意顺序处理任意数组中的任意值，无论它们最初提供的顺序如何。这是因为每个单独的数组在与其他数组进行比较之前首先进行排序。例如：

    <?php
    $arrayA     = ["string", 1];
    $arrayB = [["value" => 1]];
    // $item1 和 $item2 可以是“string”、1 或 ["value" => 1]
    $compareFunc = static function ($item1, $item2) {
    $value1 = is_string($item1) ? strlen($item1) : (is_array($item1) ? $item1["value"] : $item1);
    $value2 = is_string($item2) ? strlen($item2) : (is_array($item2) ? $item2["value"] : $item2);
    return     $value1 <=> $value2;
    };
    ?>

    返回值

    返回 array 里没有出现在其他参数里的所有值。

    示例

    示例 #1 array_udiff() 使用 stdClass 对象的示例

    <?php
    // 要对比的数组
    $array1 = array(new stdClass, new stdClass,
    new     stdClass, new stdClass,
    );

    $array2 = array(
    new     stdClass, new stdClass,
    );

    // 为每个对象设置一些属性
    $array1[0]->width = 11; $array1[0]->height = 3;
    $array1[1]->width = 7; $array1[1]->height = 1;
    $array1[2]->width = 2; $array1[2]->height = 9;
    $array1[3]->width = 5; $array1[3]->height = 7;

    $array2[0]->width = 7; $array2[0]->height = 5;
    $array2[1]->width = 9; $array2[1]->height = 2;

    function     compare_by_area($a, $b) {
    $areaA = $a->width * $a->height;
    $areaB = $b->width * $b->height;

    if (    $areaA < $areaB) {
    return -    1;
    } elseif (    $areaA > $areaB) {
    return     1;
    } else {
    return     0;
    }
    }

    print_r(array_udiff($array1, $array2, 'compare_by_area'));
    ?>

    以上示例会输出：

    Array
(
    [0] => stdClass Object
        (
            [width] => 11
            [height] => 3
        )

    [1] => stdClass Object
        (
            [width] => 7
            [height] => 1
        )

)

    示例 #2 array_udiff() 使用 DateTime 对象的示例

    <?php
    class MyCalendar {
    public     $free = array();
    public     $booked = array();

    public function     __construct($week = 'now') {
    $start = new DateTime($week);
    $start->modify('Monday this week midnight');
    $end = clone $start;
    $end->modify('Friday this week midnight');
    $interval = new DateInterval('P1D');
    foreach (new     DatePeriod($start, $interval, $end) as $freeTime) {
    $this->free[] = $freeTime;
    }
    }

    public function     bookAppointment(DateTime $date, $note) {
    $this->booked[] = array('date' => $date->modify('midnight'), 'note' => $note);
    }

    public function     checkAvailability() {
    return     array_udiff($this->free, $this->booked, array($this, 'customCompare'));
    }

    public function     customCompare($free, $booked) {
    if (    is_array($free)) $a = $free['date'];
    else     $a = $free;
    if (    is_array($booked)) $b = $booked['date'];
    else     $b = $booked;
    if (    $a == $b) {
    return     0;
    } elseif (    $a > $b) {
    return     1;
    } else {
    return -    1;
    }
    }
    }

    // 为每周日程创建日历
    $myCalendar = new MyCalendar;

    // 为本周预约一些日程
    $myCalendar->bookAppointment(new DateTime('Monday this week'), "Cleaning GoogleGuy's apartment.");
    $myCalendar->bookAppointment(new DateTime('Wednesday this week'), "Going on a snowboarding trip.");
    $myCalendar->bookAppointment(new DateTime('Friday this week'), "Fixing buggy code.");

    // 通过对比 $booked 日期和 $free 日期获取空闲的天数
    echo "I'm available on the following days this week...\n\n";
    foreach (    $myCalendar->checkAvailability() as $free) {
    echo     $free->format('l'), "\n";
    }
    echo     "\n\n";
    echo     "I'm busy on the following days this week...\n\n";
    foreach (    $myCalendar->booked as $booked) {
    echo     $booked['date']->format('l'), ": ", $booked['note'], "\n";
    }
    ?>

    以上示例会输出：

    I'm available on the following days this week...

Tuesday
Thursday


I'm busy on the following days this week...

Monday: Cleaning GoogleGuy's apartment.
Wednesday: Going on a snowboarding trip.
Friday: Fixing buggy code.

    注释

    注意: 注意本函数只检查了多维数组中的一维。当然，可以用 array_udiff($array1[0], $array2[0], "data_compare_func"); 来检查更深的维度。

    参见

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    User Contributed Notes 9 notes

    up
    35
    Colin
    18 years ago
    I think the example given here using classes is convoluting things too much to demonstrate what this function does.

    array_udiff() will walk through array_values($a) and array_values($b) and compare each value by using the passed in callback function.

    To put it another way, array_udiff() compares $a[0] to $b[0], $b[1], $b[2], and $b[3] using the provided callback function.  If the callback returns zero for any of the comparisons then $a[0] will not be in the returned array from array_udiff().  It then compares $a[1] to $b[0], $b[1], $b[2], and $b[3].  Then, finally, $a[2] to $b[0], $b[1], $b[2], and $b[3].

    For example, compare_ids($a[0], $b[0]) === -5 while compare_ids($a[1], $b[1]) === 0.  Therefore, $a[1] is not returned from array_udiff() since it is present in $b.

    <?
    $a     = array(
            array(
                        'id' => 10,
                        'name' => 'John',
                        'color' => 'red',
            ),
            array(
                        'id' => 20,
                        'name' => 'Elise',
                        'color' => 'blue',
            ),
            array(
                        'id' => 30,
                        'name' => 'Mark',
                        'color' => 'red',
            ),
    );

    $b = array(
            array(
                        'id' => 15,
                        'name' => 'Nancy',
                        'color' => 'black',
            ),
            array(
                        'id' => 20,
                        'name' => 'Elise',
                        'color' => 'blue',
            ),
            array(
                        'id' => 30,
                        'name' => 'Mark',
                        'color' => 'red',
            ),
            array(
                        'id' => 40,
                        'name' => 'John',
                        'color' => 'orange',
            ),
    );

    function     compare_ids($a, $b)
    {
        return (    $a['id'] - $b['id']);
    }
    function     compare_names($a, $b)
    {
        return     strcmp($a['name'], $b['name']);
    }

    $ret = array_udiff($a, $b, 'compare_ids');
    var_dump($ret);

    $ret = array_udiff($b, $a, 'compare_ids');
    var_dump($ret);

    $ret = array_udiff($a, $b, 'compare_names');
    var_dump($ret);
    ?>

    Which returns the following.

    In the first return we see that $b has no entry in it with an id of 10.
    <?
    array(1) {
      [    0]=>
      array(    3) {
        [    "id"]=>
            int(10)
        [    "name"]=>
            string(4) "John"
            ["color"]=>
            string(3) "red"
          }
    }
    ?>

    In the second return we see that $a has no entry in it with an id of 15 or 40.
    <?
    array(2) {
      [    0]=>
      array(    3) {
        [    "id"]=>
            int(15)
        [    "name"]=>
            string(5) "Nancy"
            ["color"]=>
            string(5) "black"
          }
      [    3]=>
      array(    3) {
        [    "id"]=>
            int(40)
        [    "name"]=>
            string(4) "John"
            ["color"]=>
            string(6) "orange"
          }
    }
    ?>

    In third return we see that all names in $a are in $b (even though the entry in $b whose name is 'John' is different, the anonymous function is only comparing names).
    <?
    array(0) {
    }
    ?>
    up
    12
    napcoder
    8 years ago
    Note that the compare function is used also internally, to order the arrays and choose which element compare against in the next round.

    If your compare function is not really comparing (ie. returns 0 if elements are equals, 1 otherwise), you will receive an unexpected result.
    up
    3
    grantwparks at gmail dot com
    16 years ago
    Re: "convoluted"

    I think the point being made is that array_udiff() can be used not only for comparisons between homogenous arrays, as in your example (and definitely the most common need), but it can be used to compare heterogeneous arrays, too.

    Consider:

    <?php
    function compr_1($a, $b) {
            $aVal = is_array($a) ? $a['last_name'] : $a;
            $bVal = is_array($b) ? $b['last_name'] : $b;
        return     strcasecmp($aVal, $bVal);
    }

    $aEmployees = array(
        array(    'last_name'  => 'Smith',
                    'first_name' => 'Joe',
                    'phone'      => '555-1000'),
        array(    'last_name'  => 'Doe',
                    'first_name' => 'John',
                    'phone'      => '555-2000'),
        array(    'last_name'  => 'Flagg',
                    'first_name' => 'Randall',
                    'phone'      => '666-1000')
        );

    $aNames = array('Doe', 'Smith', 'Johnson');
       
    $result = array_udiff($aEmployees, $aNames, "compr_1");

    print_r($result);
    ?>

    Allowing me to get the "employee" that's not in the name list:

    Array ( [2] => Array ( [last_name] => Flagg [first_name] => Randall [phone] => 666-1000 ) )

    Something interesting to note, is that the two arguments to the compare function don't correspond to array1 and array2.  That's why there has to be logic in it to handle that either of the arguments might be pointing to the more complex employee array.  (Found this out the hard way.)
    up
    12
    adam dot jorgensen dot za at gmail dot com
    16 years ago
    It is not stated, by this function also diffs array1 to itself, removing any duplicate values...
    up
    10
    b4301775 at klzlk dot com
    13 years ago
    Quick example for using array_udiff to do a multi-dimensional diff

    Returns values of $arr1 that are not in $arr2

    <?php
    $arr1     = array( array('Bob', 42), array('Phil', 37), array('Frank', 39) );
           
    $arr2 = array( array('Phil', 37), array('Mark', 45) );
           
    $arr3 = array_udiff($arr1, $arr2, create_function(
            '$a,$b',
            'return strcmp( implode("", $a), implode("", $b) ); ')
        );
           
    print_r($arr3);
    ?>

    Output:

    Array
    (
        [0] => Array
            (
                [0] => Bob
                [1] => 42
            )

        [2] => Array
            (
                [0] => Frank
                [1] => 39
            )

    )
    1

    Hope this helps someone
    up
    0
    Jorge Morales (morales2k)
    5 years ago
    I find it that this is an ideal place to apply the spaceship operator, but it was not used in the examples.

    Here is Example#1 using the spaceship operator in the comparison function.

        <?php
            // Arrays to compare
            $array1 = array(new stdclass, new stdclass,
                        new     stdclass, new stdclass,
                       );

            $array2 = array(
                        new     stdclass, new stdclass,
                       );

            // Set some properties for each object
            $array1[0]->width = 11; $array1[0]->height = 3;
            $array1[1]->width = 7;  $array1[1]->height = 1;
            $array1[2]->width = 2;  $array1[2]->height = 9;
            $array1[3]->width = 5;  $array1[3]->height = 7;

            $array2[0]->width = 7;  $array2[0]->height = 5;
            $array2[1]->width = 9;  $array2[1]->height = 2;

        function     compare_by_area($a, $b) {
                $areaA = $a->width * $a->height;
                $areaB = $b->width * $b->height;
       
            return     $areaA <=> $areaB;
        }

            print_r(array_udiff($array1, $array2, 'compare_by_area'));
            ?>

    The output is:
        Array
        (
            [0] => stdClass Object
                (
                    [width] => 11
                    [height] => 3
                )
       
            [1] => stdClass Object
                (
                    [width] => 7
                    [height] => 1
                )
       
        )

    I find it is pretty awesome you can substitute all of these lines:
        if ($areaA < $areaB) {
            return -1;
        } elseif ($areaA > $areaB) {
            return 1;
        } else {
            return 0;
        }

    with just:

        return $areaA <=> $areaB;

    Neat!
    up
    0
    dmhouse at gmail dot com
    19 years ago
    Very easy way of achieving a case-insensitive version of array_diff (or indeed array_diff_assoc, array_intersect or any of these types of functions which have a similar function that takes a callback function as one of their parameters):

    array_udiff($array1, $array2, 'strcasecmp');

    This works because strcasecmp() compares two strings case-insensitively, as compared to the array_diff() which compares two strings by using the == operator, which is case-sensitive.
    up
    -1
    jared
    15 years ago
    Note that php does the string conversion *before* sending the values to the callback function.
    up
    -2
    aidan at php dot net
    20 years ago
    This functionality is now implemented in the PEAR package PHP_Compat.

    More information about using this function without upgrading your version of PHP can be found on the below link:

    http://pear.php.net/package/PHP_Compat
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