WordPress at a glance
function is not described

WP::build_query_string() public WP 2.0.0

Sets the query string property based off of the query variable property.

The 'query_string' filter is deprecated, but still works. Plugins should use the 'request' filter instead.

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

Hooks from the method
Return

null. Null. Nothing.

Usage

global $wp;
$wp->build_query_string();

Changelog

Since 2.0.0 Introduced.

Code of WP::build_query_string() WP 5.7

<?php
public function build_query_string() {
	$this->query_string = '';
	foreach ( (array) array_keys( $this->query_vars ) as $wpvar ) {
		if ( '' != $this->query_vars[ $wpvar ] ) {
			$this->query_string .= ( strlen( $this->query_string ) < 1 ) ? '' : '&';
			if ( ! is_scalar( $this->query_vars[ $wpvar ] ) ) { // Discard non-scalars.
				continue;
			}
			$this->query_string .= $wpvar . '=' . rawurlencode( $this->query_vars[ $wpvar ] );
		}
	}

	if ( has_filter( 'query_string' ) ) {  // Don't bother filtering and parsing if no plugins are hooked in.
		/**
		 * Filters the query string before parsing.
		 *
		 * @since 1.5.0
		 * @deprecated 2.1.0 Use {@see 'query_vars'} or {@see 'request'} filters instead.
		 *
		 * @param string $query_string The query string to modify.
		 */
		$this->query_string = apply_filters_deprecated(
			'query_string',
			array( $this->query_string ),
			'2.1.0',
			'query_vars, request'
		);
		parse_str( $this->query_string, $this->query_vars );
	}
}