如何仅使用数字键提取数组值？

Question

Considering array like:

$arr = array(
  'key' => 'foo'
  'key2' => 'bar',
   0 => 'num_foo',
   1 => 'num_bar'

);

How to extract values under 0 & 1? (Besides using for loop). Maybe any standard function do the job?

Answer 1

If you’re using a PHP version >= 5.6, you can use array_filter, with the flag that tells it to pass the key to the callback function.

$arr = array(
  'key' => 'foo',
  'key2' => 'bar',
   0 => 'num_foo',
   1 => 'num_bar'
);

$new_array = array_filter($arr, function($key) {
  return is_numeric($key);
}, ARRAY_FILTER_USE_KEY);

var_dump($new_array);

https://3v4l.org/qfar9

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Edit: As Robbie pointed out, using is_numeric is the better choice here. (Previously my example used is_int.)

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Edit 2: Perhaps is_int is actually the better choice here. is_numeric would return true for values such as +0123.45e6, or hexadecimal/binary number notations as well – not sure if that’s desired.

is_int would normally return false for a value such as '1'. It works here, because we are dealing with arrays – and PHP automatically converts array keys to integer, if they are an “integer string.”