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function is not described

WP_Rewrite::preg_index() public WP 1.5.0

Indexes for matches for usage in preg_*() functions.

The format of the string is, with empty matches property value, '$NUM'. The 'NUM' will be replaced with the value in the $number parameter. With the matches property not empty, the value of the returned string will contain that value of the matches property. The format then will be '$MATCHES[NUM]', with MATCHES as the value in the property and NUM the value of the $number parameter.

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

No Hooks.

Return

String.

Usage

global $wp_rewrite;
$wp_rewrite->preg_index( $number );
$number(int) (required)
Index number.

Changelog

Since 1.5.0 Introduced.

Code of WP_Rewrite::preg_index() WP 5.5.3

<?php
public function preg_index( $number ) {
	$match_prefix = '$';
	$match_suffix = '';

	if ( ! empty( $this->matches ) ) {
		$match_prefix = '$' . $this->matches . '[';
		$match_suffix = ']';
	}

	return "$match_prefix$number$match_suffix";
}