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 ImmVector containing the values of the current Pair that meet a supplied condition

public function filter(
  (function(mixed): bool) $callback,
): ImmVector<mixed>;

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

• Examples

Parameters

• (function(mixed): bool) $callback - The callback containing the condition to apply to the current Pair values.

Returns

• ImmVector<mixed> - an ImmVector containing the values after a user-specified condition is applied.

Examples

$p = Pair {-1.5, null};

$v = $p->filter($value ==> $value !== null);
\var_dump($v);