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filter

Note

This is a point-in-time snapshot of the API documentation from January 2026. Going forward, we will not be maintaining a public copy of these references, and recommend users to refer to the built-in signature helpers available in the Hack LSP instead for complete and up-to-date information.

Returns a Set containing the values of the current Set that meet a supplied condition applied to each value

public function filter(
  (function(Tv): bool) $callback,
): Set<Tv>;

Only values that meet a certain criteria are affected by a call to filter(), while all values are affected by a call to map().

Guide​

Parameters​

  • (function(Tv): bool) $callback

Returns​

  • Set<Tv> - a Set containing the values after a user-specified condition is applied.

Examples​

$colors = Set {'red', 'green', 'blue', 'yellow'};

// Create a Set of colors that contain the letter 'l'
$l_colors = $colors->filter($color ==> \strpos($color, 'l') !== false);
\var_dump($l_colors);