PHP - get all keys from a array that start with a certain string

Question

I have an array that looks like this:

array(
  \'abc\' => 0,
  \'foo-bcd\' => 1,
  \'foo-def\' => 1,
  \'foo-xyz\' => 0,
  // ...
)

Answer 1

From PHP5.6, the array keys can be the sole subject of the filtration by using the ARRAY_FILTER_USE_KEY constant/flag.

From PHP7.4, arrow functions make custom functions more concise and allow values to be passed into the custom function's scope without use().

From PHP8, str_starts_with() can take the place of strpos(...) === 0

Code: (Demo)

$array = [
  'abc' => 0,
  'foo-bcd' => 1,
  'foo-def' => 1,
  'foo-xyz' => 0,
];

$prefix = 'foo';

var_export(
    array_filter(
        $array,
        fn($key) => str_starts_with($key, $prefix),
        ARRAY_FILTER_USE_KEY
    )
);

Output:

array (
  'foo-bcd' => 1,
  'foo-def' => 1,
  'foo-xyz' => 0,
)