Función que devuelve la URL de una petición HTTP a partir de las variables de $_SERVER.

url_origin.php

<?php
function url_origin( $s, $use_forwarded_host = false )
{
    $ssl      = ( ! empty( $s['HTTPS'] ) && $s['HTTPS'] == 'on' );
    $sp       = strtolower( $s['SERVER_PROTOCOL'] );
    $protocol = substr( $sp, 0, strpos( $sp, '/' ) ) . ( ( $ssl ) ? 's' : '' );
    $port     = $s['SERVER_PORT'];
    $port     = ( ( ! $ssl && $port=='80' ) || ( $ssl && $port=='443' ) ) ? '' : ':'.$port;
    $host     = ( $use_forwarded_host && isset( $s['HTTP_X_FORWARDED_HOST'] ) ) ? $s['HTTP_X_FORWARDED_HOST'] : ( isset( $s['HTTP_HOST'] ) ? $s['HTTP_HOST'] : null );
    $host     = isset( $host ) ? $host : $s['SERVER_NAME'] . $port;
    return $protocol . '://' . $host;
}

function full_url( $s, $use_forwarded_host = false )
{
    return url_origin( $s, $use_forwarded_host ) . $s['REQUEST_URI'];
}

/* =========================
Ejemplo de uso

$direccion_url = full_url( $_SERVER );
echo direccion_url;
================================ */
?>