How to Convert a Relative Path to an Absolute URL Using PHP?

Transforming Relative Paths into Absolute URLs with PHP

Converting relative paths into absolute URLs is essential for working with web-based resources. This task can be accomplished using PHP, a widely-used scripting language for web development.

How to Convert a Relative Path to an Absolute URL Using PHP:

To achieve this conversion, you can utilize the rel2abs() function:

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;
}

Explanation:

1. Check if the relative path is already an absolute URL (contains a scheme).
2. Concatenate queries or anchors with the base URL.
3. Parse the base URL into its scheme, host, and path components.
4. Convert the provided relative path into a "dirty" absolute URL.
5. Iteratively replace patterns like "//" or "/./" or "/foo/../" with "/" to clean up the absolute URL.
6. Return the cleaned absolute URL.

Usage:

You can utilize this function to transform any relative path into its corresponding absolute URL. For example, the following snippets depict how to transform a relative path into an absolute URL:

$rel_path = "images/profile.jpg";
$base_url = "https://example.com/";

$abs_url = rel2abs($rel_path, $base_url); // Output: "https://example.com/images/profile.jpg"

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