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function is not described

WP_List_Util::filter() public WP 4.7.0

Filters the list, based on a set of key => value arguments.

Retrieves the objects from the list that match the given arguments. Key represents property name, and value represents property value.

If an object has more properties than those specified in arguments, that will not disqualify it. When using the 'AND' operator, any missing properties will disqualify it.

{} It's a method of the class: WP_List_Util{}

No Hooks.

Return

Array. Array of found values.

Usage

$WP_List_Util = new WP_List_Util();
$WP_List_Util->filter( $args, $operator );
$args(array)
An array of key => value arguments to match against each object.
Default: empty array
$operator(string)
The logical operation to perform. 'AND' means all elements from the array must match. 'OR' means only one element needs to match. 'NOT' means no elements may match.
Default: 'AND'

Changelog

Since 4.7.0 Introduced.

Code of WP_List_Util::filter() WP 5.8

<?php
public function filter( $args = array(), $operator = 'AND' ) {
	if ( empty( $args ) ) {
		return $this->output;
	}

	$operator = strtoupper( $operator );

	if ( ! in_array( $operator, array( 'AND', 'OR', 'NOT' ), true ) ) {
		return array();
	}

	$count    = count( $args );
	$filtered = array();

	foreach ( $this->output as $key => $obj ) {
		$matched = 0;

		foreach ( $args as $m_key => $m_value ) {
			if ( is_array( $obj ) ) {
				// Treat object as an array.
				if ( array_key_exists( $m_key, $obj ) && ( $m_value == $obj[ $m_key ] ) ) {
					$matched++;
				}
			} elseif ( is_object( $obj ) ) {
				// Treat object as an object.
				if ( isset( $obj->{$m_key} ) && ( $m_value == $obj->{$m_key} ) ) {
					$matched++;
				}
			}
		}

		if ( ( 'AND' === $operator && $matched === $count )
			|| ( 'OR' === $operator && $matched > 0 )
			|| ( 'NOT' === $operator && 0 === $matched )
		) {
			$filtered[ $key ] = $obj;
		}
	}

	$this->output = $filtered;

	return $this->output;
}