Filter turns regular (lists) arrays to associative (hashmaps) array

[nreynis]

When you filter an array, it may become 'sparse'. PHP deals with this situation by turning it to an associative array:
https://eval.in/916518

<?php
$a1 = ['a', 'z', 'e', 'r', 't', 'y', 'u', 'i', 'o', 'p', 'q', 's', 'd'];
$a2 = ['a', 'z', 'e', 'r', 't', 'y', 'u', 'i', 'o'];

echo json_encode(array_filter($a1, function($i){ return $i != 's'; }));
echo json_encode(array_filter($a2, function($i){ return $i != 's'; }));

{"0":"a","1":"z","2":"e","3":"r","4":"t","5":"y","6":"u","7":"i","8":"o","9":"p","10":"q","12":"d"}
["a","z","e","r","t","y","u","i","o"]

This is really disturbing and unintuitive, no other language (AFAIK) do that. I know PHP always had this permanent confusion between lists and maps, but this doesn't feel right: if I filter a list I should get a filtered list in return.

Would you consider adding a boolean argument forceList or adding a filterList method who always return array_values in the internal state ?

[florianeckerstorfer]

Yes, I would add such a functionality. Since PHP can filter both maps and lists I would prefer if we add an additional function filterList(), to make the behavior more clear.

[nreynis]

Another more versatile solution would be to add a values method. So you can do something like:

$chain->filter(...)->values()->array;

Also that would be more consistent with current interface which already implements a keys method.