duanhang032796
2018-06-28 14:32 浏览 25
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array_diff_assoc文档代码的意外结果

Here is an example from PHP documentation about array_diff_assoc.

In this example you see the "a" => "green" pair is present in both arrays and thus it is not in the output from the function. Unlike this, the pair 0 => "red" is in the output because in the second argument "red" has key which is 1.

<?php
$array1 = array("a" => "green", "b" => "brown", "c" => "blue", "red");
$array2 = array("a" => "green", "yellow", "red");
$result = array_diff_assoc($array1, $array2);
print_r($result);
?>

The above example will output:

Array
(
    [b] => brown
    [c] => blue
    [0] => red
)

red is present in both arrays, but it is returned in the output of array_diff_assoc, why PHP think that red in $array1 and $array2 is different?

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2条回答 默认 最新

  • 已采纳
    doulu4316 doulu4316 2018-06-28 14:36

    That is because in the first array the index of red is 0 and in the second array the index of red is 1 so they are different.

    array_diff_assoc

    From the docs:

    Computes the difference of arrays with additional index check

    Check the vardumps:

    <?php
    
    $array1 = array("a" => "green", "b" => "brown", "c" => "blue", "red");
    $array2 = array("a" => "green", "yellow", "red");
    var_dump($array1);
    var_dump($array2);
    

    Output:

    array(4) {
      ["a"]=>
      string(5) "green"
      ["b"]=>
      string(5) "brown"
      ["c"]=>
      string(4) "blue"
      [0]=>
      string(3) "red"
    }
    array(3) {
      ["a"]=>
      string(5) "green"
      [0]=>
      string(6) "yellow"
      [1]=>
      string(3) "red"
    }
    
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  • doxrxwn2252 doxrxwn2252 2018-06-28 15:04

    The key for red in $array1 is 0:

    $array1 ( [a] => green [b] => brown [c] => blue [0] => red )

    $array2 ( [a] => green [0] => yellow [1] => red )

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