假设我们有两个数组:

$array_1 = array(
  '0' => 'zero',
  '1' => 'one',
  '2' => 'two',
  '3' => 'three',
);

$array_2 = array(
  'zero'  => '0',
  'one'   => '1',
  'two'   => '2',
  'three' => '3',
);

现在,我想在每个数组的第三个元素后插入数组('sample_key' => 'sample_value')。我该怎么做呢?


当前回答

这是一个老问题,但我在2014年发表了一篇评论,经常回到这个问题。我想我应该留下一个完整的答案。这不是最短的解决方案,但很容易理解。

在关联数组中插入一个新值,在有编号的位置,保留键并保持顺序。

$columns = array(
    'id' => 'ID',
    'name' => 'Name',
    'email' => 'Email',
    'count' => 'Number of posts'
);

$columns = array_merge(
    array_slice( $columns, 0, 3, true ),     // The first 3 items from the old array
    array( 'subscribed' => 'Subscribed' ),   // New value to add after the 3rd item
    array_slice( $columns, 3, null, true )   // Other items after the 3rd
);

print_r( $columns );

/*
Array ( 
    [id] => ID 
    [name] => Name 
    [email] => Email 
    [subscribed] => Subscribed 
    [count] => Number of posts 
)
*/

其他回答

更简洁的方法(基于使用的流动性和更少的代码)。

/**
 * Insert data at position given the target key.
 *
 * @param array $array
 * @param mixed $target_key
 * @param mixed $insert_key
 * @param mixed $insert_val
 * @param bool $insert_after
 * @param bool $append_on_fail
 * @param array $out
 * @return array
 */
function array_insert(
    array $array, 
    $target_key, 
    $insert_key, 
    $insert_val = null,
    $insert_after = true,
    $append_on_fail = false,
    $out = [])
{
    foreach ($array as $key => $value) {
        if ($insert_after) $out[$key] = $value;
        if ($key == $target_key) $out[$insert_key] = $insert_val;
        if (!$insert_after) $out[$key] = $value;
    }

    if (!isset($array[$target_key]) && $append_on_fail) {
        $out[$insert_key] = $insert_val;
    }

    return $out;
}

用法:

$colors = [
    'blue' => 'Blue',
    'green' => 'Green',
    'orange' => 'Orange',
];

$colors = array_insert($colors, 'blue', 'pink', 'Pink');

die(var_dump($colors));

试试这个===

$key_pos=0;
$a1=array("a"=>"red", "b"=>"green", "c"=>"blue", "d"=>"yellow");
$arrkey=array_keys($a1);
array_walk($arrkey,function($val,$key) use(&$key_pos) {
  if($val=='b')
    {
        $key_pos=$key;
    }
  });
$a2=array("e"=>"purple");
$newArray = array_slice($a1, 0, $key_pos, true) + $a2 +
        array_slice($a1, $key_pos, NULL, true);
print_r($newArray);

输出

Array (
      [a] => red
      [e] => purple
      [b] => green
      [c] => blue
      [d] => yellow )

你可以在foreach循环中插入元素,因为这个循环工作在原始数组的副本上,但是你必须跟踪插入的行数(在这段代码中我称之为“膨胀”):

$bloat=0;
foreach ($Lines as $n=>$Line)
    {
    if (MustInsertLineHere($Line))
        {
        array_splice($Lines,$n+$bloat,0,"string to insert");
        ++$bloat;
        }
    }

显然,您可以推广这种“膨胀”思想来处理foreach循环期间的任意插入和删除。

我这样做


    $slightly_damaged = array_merge(
        array_slice($slightly_damaged, 0, 4, true) + ["4" => "0.0"], 
        array_slice($slightly_damaged, 4, count($slightly_damaged) - 4, true)
    );

我刚刚创建了一个ArrayHelper类,它可以使数值索引变得非常容易。

class ArrayHelper
{
    /*
        Inserts a value at the given position or throws an exception if
        the position is out of range.
        This function will push the current values up in index. ex. if 
        you insert at index 1 then the previous value at index 1 will 
        be pushed to index 2 and so on.
        $pos: The position where the inserted value should be placed. 
        Starts at 0.
    */
    public static function insertValueAtPos(array &$array, $pos, $value) {
        $maxIndex = count($array)-1;

        if ($pos === 0) {
            array_unshift($array, $value);
        } elseif (($pos > 0) && ($pos <= $maxIndex)) {
            $firstHalf = array_slice($array, 0, $pos);
            $secondHalf = array_slice($array, $pos);
            $array = array_merge($firstHalf, array($value), $secondHalf);
        } else {
            throw new IndexOutOfBoundsException();
        }

    }
}

例子:

$array = array('a', 'b', 'c', 'd', 'e');
$insertValue = 'insert';
\ArrayHelper::insertValueAtPos($array, 3, $insertValue);

开始$数组:

Array ( 
    [0] => a 
    [1] => b 
    [2] => c 
    [3] => d 
    [4] => e 
)

结果:

Array ( 
    [0] => a 
    [1] => b 
    [2] => c 
    [3] => insert 
    [4] => d 
    [5] => e 
)