Question

我该怎么做：

array(2) {
  [0] => array(1) {
    ["bleh"] => int(109720)
  }
  [1] => array(1) {
    ["bleh"] => int(112439)
  }
}

最有效率？

array(2) {
  0 => 109720,
  1 => 112439
}

Answer 1

使用array_map。

$a = array_map(function($e) { return $e['bleh']; }, $a);

Answer 2

尝试reset

  $result = array_map("reset", $a);

Answer 3

如果您需要快速解决方案（良好的执行速度），那么：

$a = /* the original array */;
$b = array();
foreach ($a as $value) {
    $b[] = $value['bleh'];
}

Answer 4

我无法按照以下评论中给出的测量结果进行konforces回答，但是这个测试的速度比使用refs的foreach快得多：

$c=count($array);
for(
  $i=0;
  $i<$c
  ;
  $array[$i]=$array[$i]['bleh'],
  $i++
);

不会说实际测量它是微不足道的，时间会根据哪一个先来改变一点，这是一个有1000万成员的数组：

foreach ref: 4.192161
foreach key: 4.383342
foreach copy: 4.222771
array_map lambda: 12.240275
array_map reset: 16.401093
for key: 3.459406
for copy: 4.690722

脚本：

ini_set('memory_limit', -1); // wer're going to consume a lot.
$arrayCount = 10000000;

$test = 'just run';
$array = array_fill(0, $arrayCount, array("bleh" => 109720,));
$array = end($array);
$array = array_fill(0, $arrayCount, array("bleh" => 109720,));
$array = array_map(function(){}, $array);

$test = 'foreach ref';
$array = array_fill(0, $arrayCount, array("bleh" => 109720,));
$start = microtime(1);
foreach($array as &$v) $v = $v['bleh'];
unset($v);
$diff = microtime(1)-$start;
$tests[$test] = $diff;
printf("%s: %f\n", $test, $diff);

$test = 'foreach key';
$array = array_fill(0, $arrayCount, array("bleh" => 109720,));
$start = microtime(1);
foreach($array as $k => $v) $array[$k] = $v['bleh'];
$diff = microtime(1)-$start;
$tests[$test] = $diff;

printf("%s: %f\n", $test, $diff);
$test = 'foreach copy';
$array = array_fill(0, $arrayCount, array("bleh" => 109720,));
$start = microtime(1);
foreach($array as $k => $v) $arrayb[] = $v['bleh'];
$diff = microtime(1)-$start;
$tests[$test] = $diff;
unset($arrayb);
printf("%s: %f\n", $test, $diff);

$test = 'array_map lambda';
$array = array_fill(0, $arrayCount, array("bleh" => 109720,));
$start = microtime(1);
$array = array_map(function($e) { return $e['bleh']; }, $array);
$diff = microtime(1)-$start;
$tests[$test] = $diff;
printf("%s: %f\n", $test, $diff);

$test = 'array_map reset';
$array = array_fill(0, $arrayCount, array("bleh" => 109720,));
$start = microtime(1);
$array = array_map('reset', $array);
foreach($array as $k => $v) $arrayb[] = $v['bleh'];
$diff = microtime(1)-$start;
$tests[$test] = $diff;
printf("%s: %f\n", $test, $diff);

$test = 'for key';
$array = array_fill(0, $arrayCount, array("bleh" => 109720,));
$start = microtime(1);
for($i=0,$c=count($array);$i<$c;$array[$i]=$array[$i]['bleh'],++$i);
$diff = microtime(1)-$start;
$tests[$test] = $diff;
printf("%s: %f\n", $test, $diff);

$test = 'for copy';
$array = array_fill(0, $arrayCount, array("bleh" => 109720,));
$start = microtime(1);
for($i=0,$c=count($array);$i<$c;$arrayb[]=$array[$i]['bleh'],++$i);
$diff = microtime(1)-$start;
$tests[$test] = $diff;
unset($arrayb);
printf("%s: %f\n", $test, $diff);

Answer 5

<?php
$all = array(
    array( "one"    => 1),
    array( "two"    => 2),
    array( "three"  => 3)
);

function getKey($item)
{
    return key($item);
}

function getVal($item)
{
    return $item[key($item)];
}
$keys   = array_map("getKey", $all);
$values = array_map("getVal", $all);
print_r($keys);
print_r($values);

OUTPUT:

Array (
    [0] => one
    [1] => two
    [2] => three ) 
Array (
    [0] => 1
    [1] => 2
    [2] => 3 )

从阵列数组转换为单个数组

5 个答案: