CODEWITHSUNDEEP
phpurlrelative-pathabsolute-pathrelative-url
Yarin
Yarin

Reputation: 183939

Checking for relative vs absolute paths/URLs in PHP

I need to implement functions to check whether paths and urls are relative, absolute, or invalid (invalid syntactically- not whether resource exists). What are the range of cases I should be looking for?

function check_path($dirOrFile) {
    // If it's an absolute path: (Anything that starts with a '/'?)
        return 'absolute';
    // If it's a relative path: 
        return 'relative';
    // If it's an invalid path:
        return 'invalid';
}

function check_url($url) {
    // If it's an absolute url: (Anything that starts with a 'http://' or 'https://'?)
        return 'absolute';
    // If it's a relative url:
        return 'relative';
    // If it's an invalid url:
        return 'invalid';
}

Upvotes: 14

Views: 19791

Answers (8)

iohnatan
iohnatan

Reputation: 21

My grain of salt based on @CIRCLE answer (Symfony FileSystem Component that checks file paths):

public function is_absolute_url( $url ) {
    if ( substr( $url, 0, 1 ) === '/' ||
        // minimun absolute url lenght 5: a://a.
        strlen( $url ) < 5
    ) {
        return false;
    }

    // chars before the first '://' in the URL are only alphabetic letters?
    $scheme = strtok( $url, '://' );
    if ( ! $scheme || // no scheme found.
        ! ctype_alpha( $scheme ) // scheme with only alphabetic letters.
    ) {
        return false;
    }

    // confirm URI has a valid scheme.
    return null !== parse_url( $url, PHP_URL_SCHEME );
}

Upvotes: 0

Luca C.
Luca C.

Reputation: 12594

If you already know that the URL is well formed:

if(strpos($uri,'://')!==false){
    //protocol: absolute url
}elseif(substr($uri,0,1)=='/'){
    //leading '/': absolute to domain name (half relative)
}else{
    //no protocol and no leading slash: relative to this page
}

Upvotes: 3

Developer
Developer

Reputation: 2895

Use:

function isAbsolute($url) {
  return isset(parse_url($url)['host']);
}

Explanation:

If the host is set, the path is absolute.

For example:

$test = [
'/link?param=1'=>parse_url('/assa?ass'),
'//aaa.com/link?param=1'=>parse_url('//assa?ass'),
'http://aaa.com/link?param=1'=>parse_url('http://as.plassa?ass')
];
var_export($test);

/* Output:
[
  "/link?param=1" => array:2 [▼ // Not absolute
    "path" => "/assa"
    "query" => "ass"
  ]
  "//aaa.com/link?param=1" => array:2 [▼ // Absolute because of host
    "host" => "assa"
    "query" => "ass"
  ]
  "http://aaa.com/link?param=1" => array:3 [▼ // Absolute because of host
    "scheme" => "http"
    "host" => "as.plassa"
    "query" => "ass"
  ]
]
*/

Upvotes: 11

Roman Zahradn&#237;k
Roman Zahradn&#237;k

Reputation: 41

Since I cannot comment on answers because of my poor reputation I have to respond to ymakux answer with the function that he copied from Drupal library.

I am using this function and I have found out that urls with query part (text after ? symbol) which contains | symbol will be evaluated to false

for example:

https://example.com/image.jpeg?fl=res,749,562,3|shr,,20|jpg,90

Will be evaluated to false.

All you have to do is add

\|

To query part of the regex so the function looks like:

public static function isAbsoluteUrl($url)
    {
        $pattern = "/^(?:ftp|https?|feed)?:?\/\/(?:(?:(?:[\w\.\-\+!$&'\(\)*\+,;=]|%[0-9a-f]{2})+:)*
        (?:[\w\.\-\+%!$&'\(\)*\+,;=]|%[0-9a-f]{2})+@)?(?:
        (?:[a-z0-9\-\.]|%[0-9a-f]{2})+|(?:\[(?:[0-9a-f]{0,4}:)*(?:[0-9a-f]{0,4})\]))(?::[0-9]+)?(?:[\/|\?]
        (?:[\w#!:\.\?\+\|=&@$'~*,;\/\(\)\[\]\-]|%[0-9a-f]{2})*)?$/xi";

        return (bool) preg_match($pattern, $url);
    }

Hope it helps someone :)

Upvotes: 4

CIRCLE
CIRCLE

Reputation: 4879

From Symfony FileSystem component to check if a path is absolute:

public function isAbsolutePath($file)
{
    return strspn($file, '/\\', 0, 1)
        || (strlen($file) > 3 && ctype_alpha($file[0])
            && substr($file, 1, 1) === ':'
            && strspn($file, '/\\', 2, 1)
        )
        || null !== parse_url($file, PHP_URL_SCHEME)
    ;
}

Upvotes: 4

ymakux
ymakux

Reputation: 3495

This function is taken from Drupal

public function is_absolute($url)
{
    $pattern = "/^(?:ftp|https?|feed):\/\/(?:(?:(?:[\w\.\-\+!$&'\(\)*\+,;=]|%[0-9a-f]{2})+:)*
    (?:[\w\.\-\+%!$&'\(\)*\+,;=]|%[0-9a-f]{2})+@)?(?:
    (?:[a-z0-9\-\.]|%[0-9a-f]{2})+|(?:\[(?:[0-9a-f]{0,4}:)*(?:[0-9a-f]{0,4})\]))(?::[0-9]+)?(?:[\/|\?]
    (?:[\w#!:\.\?\+=&@$'~*,;\/\(\)\[\]\-]|%[0-9a-f]{2})*)?$/xi";

    return (bool) preg_match($pattern, $url);
}

Upvotes: 3

Rob
Rob

Reputation: 4987

I've recently started a composer package that might be useful for checking wether URL's are relative / absolute (and more, ofcourse).

Check out the repository here: https://github.com/Enrise/UriHelper Or the composer Packagists package here: https://packagist.org/packages/enrise/urihelper

Some examples:

$uri = new \Enrise\Uri('http://usr:[email protected]:81/mypath/myfile.html?a=b&b[]=2&b[]=3#myfragment');
echo $uri->getScheme(); // http
echo $uri->getUser(); // usr
echo $uri->getPass(); // pss
echo $uri->getHost(); // example.com
echo $uri->getPort(); // 81
echo $uri->getPath(); // /mypath/myfile.html
echo $uri->getQuery(); // a=b&b[]=2&b[]=3
echo $uri->getFragment(); // myfragment
echo $uri->isSchemeless(); // false
echo $uri->isRelative(); // false

$uri->setScheme('scheme:child:scheme.VALIDscheme123:');
$uri->setPort(null);

echo $uri->getUri(); //scheme:child:scheme.VALIDscheme123:usr:[email protected]/mypath/myfile.html?a=b&b[]=2&b[]=3#myfragment

Upvotes: 2

Ofir
Ofir

Reputation: 415

Absolute Paths and URLs

You are correct, absolute URLs in Linux must start with /, so checking for a slash in the start of the path will be enough.

For URLs you need to check for http:// and https://, as you wrote, however, there are more URLs starting with ftp://, sftp:// or smb://. So it is very depending on what range of uses you want to cover.

Invalid Paths and URLs

Assuming you are referring to Linux, the only chars that are forbidden in a path are / and \0. This is actually very filesystem dependent, however, you can assume the above to be correct for most uses.

In Windows it is more complicated. You can read about it in the Path.GetInvalidPathChars Method documentation under Remarks.

URLs are more complicated than Linux paths as the only allowed chars are A-Z, a-z, 0-9, -, ., _, ~, :, /, ?, #, [, ], @, !, $, &, ', (, ), *, +, ,, ; and = (as described in another answer here).

Relative Paths and URLs

In general, paths and URLs which are neither absolute nor invalid are relative.

Upvotes: 5

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