php array_filter没有密钥保存

Question

if i filter an array with array_filter to eliminate null values, keys are preserved and this generated "holes" in the array. Eg:

The filtered version of
    [0] => 'foo'
    [1] =>  null
    [2] => 'bar'
is 
    [0] => 'foo'
    [2] => 'bar'

How can i get, instead

[0] => 'foo'
[1] => 'bar'

?

Answer 1

您可以在过滤后使用array_values来获取值。

Answer 2

Using this input:

$array=['foo',NULL,'bar',0,false,null,'0',''];

There are a few ways you could do it. Demo

It's slightly off-topic to bring up array_filter 's greedy default behavior, but if you are googling to this page, this is probably important information relevant to your project/task:

var_export(array_values(array_filter($array)));  // NOT GOOD!!!!!

Bad Output:

array (
  0 => 'foo',
  1 => 'bar',
)

---

Now for the ways that will work:

Method #1 : ( array_values() , array_filter() w/ !is_null() )

var_export(array_values(array_filter($array,function($v){return !is_null($v);})));  // good

Method #2 : ( foreach() , auto-indexed array, !==null )

foreach($array as $v){
    if($v!==null){$result[]=$v;}
}
var_export($result);  // good

Method #3 : ( array_walk() , auto-index array, !is_null() )

array_walk($array,function($v)use(&$filtered){if(!is_null($v)){$filtered[]=$v;}});
var_export($filtered);  // good

All three methods provide the following "null-free" output:

array (
  0 => 'foo',
  1 => 'bar',
  2 => 0,
  3 => false,
  4 => '0',
  5 => '',
)

---

From PHP7.4, you can even perform a "repack" like this: (the splat operator requires numeric keys)

Code: ( Demo )

$array = ['foo', NULL, 'bar', 0, false, null, '0', ''];

$array = [...array_filter($array)];

var_export($array);

Output:

array (
  0 => 'foo',
  1 => 'bar',
)

... but as it turns out, "repacking" with the splat operator is far less efficient than calling array_values() .