1

在尝试对 SplFixedArrays 进行基准测试时，我一直注意到一些奇怪的行为。以这个小代码片段为例......

<?php
$splFixedArray = new \SplFixedArray( 100000 );
echo number_format( memory_get_usage() ) . PHP_EOL;
$variable = 'Truffaut single-origin coffee wayfarers, church-key asymmetrical 90\'s trust fund hashtag before they sold out thundercats photo booth. Godard sustainable roof party keffiyeh, Odd Future chillwave mlkshk kogi VHS leggings hoodie art party next level dreamcatcher yr. Blog american apparel aesthetic tattooed farm-to-table, stumptown viral whatever mixtape raw denim Williamsburg skateboard flexitarian actually tofu. Echo Park lomo disrupt PBR, jean shorts irony fingerstache blog kale chips. Street art iPhone PBR fingerstache Bushwick Cosby sweater. McSweeney\'s mumblecore semiotics, twee quinoa tofu +1 fingerstache pop-up. Echo Park bitters disrupt irony. Truffaut single-origin coffee wayfarers, church-key asymmetrical 90\'s trust fund hashtag before they sold out thundercats photo booth. Godard sustainable roof party keffiyeh, Odd Future chillwave mlkshk kogi VHS leggings hoodie art party next level dreamcatcher yr. Blog american apparel aesthetic tattooed farm-to-table, stumptown viral whatever mixtape raw denim Williamsburg skateboard flexitarian actually tofu. Echo Park lomo disrupt PBR, jean shorts irony fingerstache blog kale chips. Street art iPhone PBR fingerstache Bushwick Cosby sweater.';
var_dump( $variable );
for( $i = 0; $i < 100000; $i++ )
{
    $splFixedArray[ $i ] = $variable;
}
echo number_format( memory_get_usage() );

哪个输出...

1,032,080
string(1209) "Truffaut single-origin coffee wayfarers, church-key asymmetrical 90's trust fund hashtag before they sold out thundercats photo booth. Godard sustainable roof party keffiyeh, Odd Future chillwave mlkshk kogi VHS leggings hoodie art party next level dreamcatcher yr. Blog american apparel aesthetic tattooed farm-to-table, stumptown viral whatever mixtape raw denim Williamsburg skateboard flexitarian actually tofu. Echo Park lomo disrupt PBR, jean shorts irony fingerstache blog kale chips. Street art iPhone PB"...
1,032,384

现在，让我们在 for 循环的末尾添加一个简单的随机整数......

<?php
$splFixedArray = new \SplFixedArray( 100000 );
echo number_format( memory_get_usage() ) . PHP_EOL;
$variable = 'Truffaut single-origin coffee wayfarers, church-key asymmetrical 90\'s trust fund hashtag before they sold out thundercats photo booth. Godard sustainable roof party keffiyeh, Odd Future chillwave mlkshk kogi VHS leggings hoodie art party next level dreamcatcher yr. Blog american apparel aesthetic tattooed farm-to-table, stumptown viral whatever mixtape raw denim Williamsburg skateboard flexitarian actually tofu. Echo Park lomo disrupt PBR, jean shorts irony fingerstache blog kale chips. Street art iPhone PBR fingerstache Bushwick Cosby sweater. McSweeney\'s mumblecore semiotics, twee quinoa tofu +1 fingerstache pop-up. Echo Park bitters disrupt irony. Truffaut single-origin coffee wayfarers, church-key asymmetrical 90\'s trust fund hashtag before they sold out thundercats photo booth. Godard sustainable roof party keffiyeh, Odd Future chillwave mlkshk kogi VHS leggings hoodie art party next level dreamcatcher yr. Blog american apparel aesthetic tattooed farm-to-table, stumptown viral whatever mixtape raw denim Williamsburg skateboard flexitarian actually tofu. Echo Park lomo disrupt PBR, jean shorts irony fingerstache blog kale chips. Street art iPhone PBR fingerstache Bushwick Cosby sweater.';
var_dump( $variable );
for( $i = 0; $i < 100000; $i++ )
{
    $splFixedArray[ $i ] = $variable . rand();
}
echo number_format( memory_get_usage() );

导致这...

1,034,320
string(1209) "Truffaut single-origin coffee wayfarers, church-key asymmetrical 90's trust fund hashtag before they sold out thundercats photo booth. Godard sustainable roof party keffiyeh, Odd Future chillwave mlkshk kogi VHS leggings hoodie art party next level dreamcatcher yr. Blog american apparel aesthetic tattooed farm-to-table, stumptown viral whatever mixtape raw denim Williamsburg skateboard flexitarian actually tofu. Echo Park lomo disrupt PBR, jean shorts irony fingerstache blog kale chips. Street art iPhone PB"...
129,834,272

我很好奇的是为什么函数调用会导致内存使用堆积。迭代后内存不会被释放是正常的吗？

4

1 回答 1

3

这种行为是预期的。

在第一种情况下，您将多次存储相同的值，这可以实现为值的单个实例和对其的一批引用，对于给定数组中的值的情况，具有写时复制语义索引变了。

在第二种情况下，您存储了许多不同的值，这些值不能以相同的方式处理；必须为每个值的全部内容分配内存，这导致您在两种情况下看到的内存消耗存在差异。

于 2013-07-18T19:56:18.040 回答