Source

File: wp-includes/class-http.php

public static function processHeaders( $headers, $url = '' ) { // phpcs:ignore WordPress.NamingConventions.ValidFunctionName.MethodNameInvalid
		// Split headers, one per array element.
		if ( is_string( $headers ) ) {
			// Tolerate line terminator: CRLF = LF (RFC 2616 19.3).
			$headers = str_replace( "\r\n", "\n", $headers );
			/*
			 * Unfold folded header fields. LWS = [CRLF] 1*( SP | HT ) <US-ASCII SP, space (32)>,
			 * <US-ASCII HT, horizontal-tab (9)> (RFC 2616 2.2).
			 */
			$headers = preg_replace( '/\n[ \t]/', ' ', $headers );
			// Create the headers array.
			$headers = explode( "\n", $headers );
		}

		$response = array(
			'code'    => 0,
			'message' => '',
		);

		/*
		 * If a redirection has taken place, The headers for each page request may have been passed.
		 * In this case, determine the final HTTP header and parse from there.
		 */
		for ( $i = count( $headers ) - 1; $i >= 0; $i-- ) {
			if ( ! empty( $headers[ $i ] ) && false === strpos( $headers[ $i ], ':' ) ) {
				$headers = array_splice( $headers, $i );
				break;
			}
		}

		$cookies    = array();
		$newheaders = array();
		foreach ( (array) $headers as $tempheader ) {
			if ( empty( $tempheader ) ) {
				continue;
			}

			if ( false === strpos( $tempheader, ':' ) ) {
				$stack   = explode( ' ', $tempheader, 3 );
				$stack[] = '';
				list( , $response['code'], $response['message']) = $stack;
				continue;
			}

			list($key, $value) = explode( ':', $tempheader, 2 );

			$key   = strtolower( $key );
			$value = trim( $value );

			if ( isset( $newheaders[ $key ] ) ) {
				if ( ! is_array( $newheaders[ $key ] ) ) {
					$newheaders[ $key ] = array( $newheaders[ $key ] );
				}
				$newheaders[ $key ][] = $value;
			} else {
				$newheaders[ $key ] = $value;
			}
			if ( 'set-cookie' === $key ) {
				$cookies[] = new WP_Http_Cookie( $value, $url );
			}
		}

		// Cast the Response Code to an int.
		$response['code'] = intval( $response['code'] );

		return array(
			'response' => $response,
			'headers'  => $newheaders,
			'cookies'  => $cookies,
		);
	}