使用 PHP 将相对路径转换为绝对 URL

function rel2abs($rel, $base)
{
    /* return if already absolute URL */
    if (parse_url($rel, PHP_URL_SCHEME) != '') return $rel;

    /* queries and anchors */
    if ($rel[0]=='#' || $rel[0]=='?') return $base.$rel;

    /* parse base URL and convert to local variables:
       $scheme, $host, $path */
    extract(parse_url($base));

    /* remove non-directory element from path */
    $path = preg_replace('#/[^/]*$#', '', $path);

    /* destroy path if relative url points to root */
    if ($rel[0] == '/') $path = '';

    /* dirty absolute URL */
    $abs = "$host$path/$rel";

    /* replace '//' or '/./' or '/foo/../' with '/' */
    $re = array('#(/\.?/)#', '#/(?!\.\.)[^/]+/\.\./#');
    for($n=1; $n>0; $abs=preg_replace($re, '/', $abs, -1, $n)) {}

    /* absolute URL is ready! */
    return $scheme.'://'.$abs;
}

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function rel2abs( $rel, $base )
{
    /* return if already absolute URL */
    if( parse_url($rel, PHP_URL_SCHEME) != '' )
        return( $rel );

    /* queries and anchors */
    if( $rel[0]=='#' || $rel[0]=='?' )
        return( $base.$rel );

    /* parse base URL and convert to local variables:
       $scheme, $host, $path */
    extract( parse_url($base) );

    /* remove non-directory element from path */
    $path = preg_replace( '#/[^/]*$#', '', $path );

    /* destroy path if relative url points to root */
    if( $rel[0] == '/' )
        $path = '';

    /* dirty absolute URL */
    $abs = '';

    /* do we have a user in our URL? */
    if( isset($user) )
    {
        $abs.= $user;

        /* password too? */
        if( isset($pass) )
            $abs.= ':'.$pass;

        $abs.= '@';
    }

    $abs.= $host;

    /* did somebody sneak in a port? */
    if( isset($port) )
        $abs.= ':'.$port;

    $abs.=$path.'/'.$rel;

    /* replace '//' or '/./' or '/foo/../' with '/' */
    $re = array('#(/\.?/)#', '#/(?!\.\.)[^/]+/\.\./#');
    for( $n=1; $n>0; $abs=preg_replace( $re, '/', $abs, -1, $n ) ) {}

    /* absolute URL is ready! */
    return( $scheme.'://'.$abs );
}