Question

在一个阵列中清除所有价值的效率如何? 第一个例子要求我每次在第二个例子的空档中使用这一功能。

foreach ($array as $i => $value) {
    unset($array[$i]);
}

或者

foreach($blah_blah as $blah) {
    $foo = array();
    //do something
    $foo = null;
}

我不想使用<代码>unset(),因为删除了变量。

Answer 1

同Zack在以下评论中说过一样,你能够简单地利用它来进行反证。

$foo = array(); // $foo is still here

如果你想要更强有力的使用,因为如果你需要紧随时间,那么,你也会从象征桌上清除烟.。

unset($foo); // $foo is gone
$foo = array(); // $foo is here again

如果我们谈论的是非常大的表格,我可能建议

$foo = null; 
unset($foo);

since that also would clear the memory a bit better. That behavior (GC) is however not very constant and may change over PHP versions. Bear in mind that re-instantiating a structure is not the same as emptying it.

Answer 2

If you just want to reset a variable to an empty array, you can simply reinitialize it:

$foo = array();

注

$foo = array(1,2,3);
$bar = &$foo;
// ...
$foo = array(); // clear array
var_dump($bar); // array(0) { } -- bar was cleared too!

如果你想打破对它的任何提及,首先要问:

$foo = array(1,2,3);
$bar = &$foo;
// ...
unset($foo); // break references
$foo = array(); // re-initialize to empty array
var_dump($bar); // array(3) { 1, 2, 3 } -- $bar is unchanged

Answer 3

如果你需要原始阵列的提及,那么确定变量是一种冰 way,

To make clear what I mean: If you have a function wich uses the reference of the array, for example a sorting function like

function special_sort_my_array(&$array) { $temporary_list = create_assoziative_special_list_out_of_array($array); sort_my_list($temporary_list); unset($array); foreach($temporary_list as $k => $v) { $array[$k] = $v; } }

它没有工作! 此处仔细看,<代码>unset删除了这一提法,因此,可变的<代码>$array再次创建并正确填满,但数值不能从职能外取用。

因此,如果你有参考,你需要使用<条码>$array = 阵列()而不是<条码>unset,即使该编码不干净,也难以理解。

Answer 4

I d say the first, if the array is associative. If not, use a for loop:

for ($i = 0; $i < count($array); $i++) { unset($array[$i]); }

尽可能使用

$array = array();

最好将阵列重新定位为空阵。

Answer 5

Isn t unset( 够好吗?

unset($array);

Answer 6

How about $array_name = array(); ?

Answer 7

Use array_splice to empty an array and retain the reference:

array_splice($myArray, 0);

Answer 8

i have used unset() to clear the array but i have come to realize that unset() will render the array null hence the need to re-declare the array like for example

<?php 
    $arr = array();
    array_push($arr , "foo");
    unset($arr); // this will set the array to null hence you need the line below or redeclaring it.
    $arr  = array();

    // do what ever you want here
?>

Answer 9

也许简单、经济的方式(没有迹象可使用)。

$array = [];

We can read in php manual :

到PHP5.4为止,你还可以使用短阵列合成物,用[]取代阵列。

Answer 10

I see this questions is realla old, but for that problem I wrote a recursive function to unset all values in an array. Recursive because its possible that values from the given array are also an array. So that works for me:

function empty_array(& $complete_array) {
    foreach($complete_array as $ckey => $cvalue)
    {
        if (!is_array($cvalue)) {
            $complete_array[$ckey] = "";
        } else {
            empty_array( $complete_array[$ckey]);
        }

    }
    return $complete_array;

}

这样一来,就有了所有关键和次级分支的阵列,而是空的价值观。

Answer 11

The unset function is useful when the garbage collector is doing its rounds while not having a lunch break;

然而,不定的职能只是销毁了数据的不同参考资料,而数据仍存在于记忆中,而PHP认为,尽管不再有数据点,但记忆在使用中。

Solution: Assign null to your variables to clear the data, at least until the garbage collector gets a hold of it.

$var = null;

而随后又以类似方式加以 un弄!

unset($var);

Answer 12

员额没有真正回答这个问题。保持关键因素和清理价值观是问题的重点。

foreach($resultMasterCleaned[ header ] as $ekey => $eval) {
    $resultMasterCleaned[$key][$eval] = "";                 
}

如同两种维权阵列一样,持有特别志愿人员的价值观,并row开一行。选择途径似乎是唯一的途径。

Answer 13

[] is nearly 30% faster then as array() similar as pushing new element to array $array[] = $newElement then array_push($array, $newElement) (keep in mind array_push is slower only for single or 2 new elements)

Reason is we skip overhead function to call those

购买力平价阵列在方法和可变声明中的[ ]

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