blocks|key|1336024|text|您可以利用函数在返回时取消对结果的引用这一事实，例如，在这里，$array_by_myclone将仍然引用$original+($array_by_myclone[0][0]+==+'foo')，而$array_by_assignment将具有克隆值($array_by_assignment[0][0]+==+'bar')。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1336025|$original+=+'foo';
$array_of_reference+=+array(&$original);

function+myclone($value)
{
++return+$value;
}

$array_by_myclone+=+array();
$array_by_myclone[]+=+array_map('myclone',+$array_of_reference);

$array_by_assignment+=+array();
$array_by_assignment[]+=+$array_of_reference;

$original+=+'bar';

var_dump($array_by_myclone[0][0]);+//+foo,+values+were+cloned+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
var_dump($array_by_assignment[0][0]);+//+bar,+still+a+reference+++++++++++++++++++++|code-block|syntax|javascript|1336026|编辑:我想检查说unserialize(serialize())更快的评论是否正确，所以我用php5.5做了测试，结果证明这是错误的:使用序列化方法即使是在小数据集的情况下也会更慢，而且你拥有的数据越多，它就会变得越慢。|1336027|lepidosteus@server:~$+php+-v
PHP+5.5.1-1~dotdeb.1+(cli)+(built:+Aug++3+2013+22:19:30)+
Copyright+(c)+1997-2013+The+PHP+Group
Zend+Engine+v2.5.0,+Copyright+(c)+1998-2013+Zend+Technologies
++++with+Zend+OPcache+v7.0.2-dev,+Copyright+(c)+1999-2013,+by+Zend+Technologies
lepidosteus@server:~$+php+reference.php+1
myclone:+++0.000010+seconds
serialize:+0.000012+seconds
lepidosteus@server:~$+php+reference.php+1000000
myclone:+++0.398540+seconds
serialize:+0.706631+seconds|1336028|使用的代码：|1336029|<?php
$iterations+=+1000000;
if+(isset($argv[1])+&&+is_numeric($argv[1]))+{
++$iterations+=+max(1,+(int)$argv[1]);
}

$items+=+array();
for+($i+=+0;+$i+<+$iterations;+$i%2B%2B)+{
++$items[]+=+'item+number+'.$i;
}

$array_of_refs+=+array();
foreach+($items+as+$k+=>+$v)+{
++$array_of_refs[]+=+&$items[$k];
}

function+myclone($value)
{
++return+$value;
}

$start+=+microtime(true);

$copy+=+array_map('myclone',+$array_of_refs);

$time+=+microtime(true)+-+$start;

printf("%25-10s+%252.6f+seconds\n",+'myclone:',+$time);

$start+=+microtime(true);

$copy+=+unserialize(serialize($array_of_refs));

$time+=+microtime(true)+-+$start;

printf("%25-10s+%252.6f+seconds\n",+'serialize:',+$time);|1336030|entityMap^0|V|H|1H|9|1S|W|2R|K|3I|Z|0|0|8|O|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@$9|V|A|W|B|C]|$9|X|A|Y|B|C]|$9|Z|A|10|B|C]|$9|11|A|12|B|C]|$9|13|A|14|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|15|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|16|8|@$9|17|A|18|B|C]]|D|@]|E|$]]|$1|M|3|N|5|H|7|19|8|@]|D|@]|E|$I|J]]|$1|O|3|P|5|6|7|1A|8|@]|D|@]|E|$]]|$1|Q|3|R|5|H|7|1B|8|@]|D|@]|E|$I|J]]|$1|S|3|-4|5|6|7|1C|8|@]|D|@]|E|$]]]|T|$]]

You can use the fact that functions dereferences results when returning, for exemple here <code>$array_by_myclone</code> will still have a reference to <code>$original</code> (<code>$array_by_myclone[0][0] == 'foo'</code>) while <code>$array_by_assignment</code> will have a cloned value (<code>$array_by_assignment[0][0] == 'bar'</code>)

<pre><code>$original = 'foo';
$array_of_reference = array(&amp;$original);

function myclone($value)
{
 return $value;
}

$array_by_myclone = array();
$array_by_myclone[] = array_map('myclone', $array_of_reference);

$array_by_assignment = array();
$array_by_assignment[] = $array_of_reference;

$original = 'bar';

var_dump($array_by_myclone[0][0]); // foo, values were cloned 
var_dump($array_by_assignment[0][0]); // bar, still a reference 
</code></pre>

EDIT: I wanted to check if the comment saying <code>unserialize(serialize())</code> was faster was right so I did the test using php 5.5, and it turns out this is wrong: using the serialization method is slower even with a small dataset, and the more data you have the slower it gets.

<pre><code>lepidosteus@server:~$ php -v
PHP 5.5.1-1~dotdeb.1 (cli) (built: Aug 3 2013 22:19:30) 
Copyright (c) 1997-2013 The PHP Group
Zend Engine v2.5.0, Copyright (c) 1998-2013 Zend Technologies
 with Zend OPcache v7.0.2-dev, Copyright (c) 1999-2013, by Zend Technologies
lepidosteus@server:~$ php reference.php 1
myclone: 0.000010 seconds
serialize: 0.000012 seconds
lepidosteus@server:~$ php reference.php 1000000
myclone: 0.398540 seconds
serialize: 0.706631 seconds
</code></pre>

Code used:

<pre><code>&lt;?php
$iterations = 1000000;
if (isset($argv[1]) &amp;&amp; is_numeric($argv[1])) {
 $iterations = max(1, (int)$argv[1]);
}

$items = array();
for ($i = 0; $i &lt; $iterations; $i++) {
 $items[] = 'item number '.$i;
}

$array_of_refs = array();
foreach ($items as $k =&gt; $v) {
 $array_of_refs[] = &amp;$items[$k];
}

function myclone($value)
{
 return $value;
}

$start = microtime(true);

$copy = array_map('myclone', $array_of_refs);

$time = microtime(true) - $start;

printf("%-10s %2.6f seconds\n", 'myclone:', $time);

$start = microtime(true);

$copy = unserialize(serialize($array_of_refs));

$time = microtime(true) - $start;

printf("%-10s %2.6f seconds\n", 'serialize:', $time);
</code></pre>

blocks|key|1336071|text|不需要将array_map与serialize进行比较，因为array_map没有用处。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1336072|$original+=+array('key'=>'foo');
$array_of_reference+=+array(&$original);
function+myclone($value)
{
++return+$value;
}
$array_by_myclone+=+array();
$array_by_myclone[]+=+array_map('myclone',+$array_of_reference);

$array_by_assignment+=+array();
$array_by_assignment[]+=+$array_of_reference;

$original['key']+=+'bar';

var_dump($array_by_myclone[0][0]['key']);+//+bar,+still+a+reference+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
var_dump($array_by_assignment[0][0]['key']);+//+bar,+still+a+reference+++|code-block|syntax|javascript|1336073|array_map将回调应用于给定数组的元素，就像foreach一样。如果要复制的数组具有多个嵌套，则array_map不起作用。|1336074|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

no need to compare array_map with serialize cause array_map is not useful.

<pre><code>$original = array('key'=&gt;'foo');
$array_of_reference = array(&amp;$original);
function myclone($value)
{
 return $value;
}
$array_by_myclone = array();
$array_by_myclone[] = array_map('myclone', $array_of_reference);

$array_by_assignment = array();
$array_by_assignment[] = $array_of_reference;

$original['key'] = 'bar';

var_dump($array_by_myclone[0][0]['key']); // bar, still a reference 
var_dump($array_by_assignment[0][0]['key']); // bar, still a reference 
</code></pre>

array_map Applies the callback to the elements of the given arrays, just like foreach. if the array you want to copy has more than 1 nest, array_map does not work.

So $array is an array of which all elements are references.

I want to append this array to another array called $results (in a loop), but since they are references, PHP copies the references and $results is full of identical elements.

So far, the best working solution is: 

<pre><code>$results[] = unserialize(serialize($array));
</code></pre>

which I fear to be incredibly inefficient. Is there a better way to do this?

Deep copy of PHP array of references

所以$array是一个所有元素都是引用的数组。我想将这个数组附加到另一个名为$results的数组中(在循环中)，但因为它们是引用，所以PHP复制引用，而$results充满了相同的元素。到目前为止，最好的解决方案是：$results[] = unserialize(serialize($array));我担心这是非常...

问PHP引用数组的深层副本
EN

社区

活动

资源

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问PHP引用数组的深层副本EN

社区

活动

资源

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问PHP引用数组的深层副本
EN