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function is not described

wp_parse_url() WP 4.4.0

A wrapper for PHP's parse_url() function that handles consistency in the return values across PHP versions.

PHP 5.4.7 expanded parse_url()'s ability to handle non-absolute url's, including schemeless and relative url's with :// in the path. This function works around those limitations providing a standard output on PHP 5.2~5.4+.

Secondly, across various PHP versions, schemeless URLs starting containing a ":" in the query are being handled inconsistently. This function works around those differences as well.

Error suppression is used as prior to PHP 5.3.3, an E_WARNING would be generated when URL parsing failed.

  • Since 4.7.0 The $component parameter was added for parity with PHP's parse_url().

No Hooks.

Return

Mixed. False on parse failure; Array of URL components on success; When a specific component has been requested: null if the component doesn't exist in the given URL; a string or - in the case of PHP_URL_PORT - integer when it does. See parse_url()'s return values.

Usage

wp_parse_url( $url, $component );
$url(string) (required)
The URL to parse.
$component(int)
The specific component to retrieve. Use one of the PHP predefined constants to specify which one.
Default: -1 (= return all parts as an array)

Code of wp parse url: wp-includes/http.php VER 5.1.1

<?php
function wp_parse_url( $url, $component = -1 ) {
	$to_unset = array();
	$url      = strval( $url );

	if ( '//' === substr( $url, 0, 2 ) ) {
		$to_unset[] = 'scheme';
		$url        = 'placeholder:' . $url;
	} elseif ( '/' === substr( $url, 0, 1 ) ) {
		$to_unset[] = 'scheme';
		$to_unset[] = 'host';
		$url        = 'placeholder://placeholder' . $url;
	}

	$parts = @parse_url( $url );

	if ( false === $parts ) {
		// Parsing failure.
		return $parts;
	}

	// Remove the placeholder values.
	foreach ( $to_unset as $key ) {
		unset( $parts[ $key ] );
	}

	return _get_component_from_parsed_url_array( $parts, $component );
}