Replace URLs in text with HTML links

Question

Here is a design though: For example is I put a link such as

http://example.com

in textarea. How do I get PHP to detect it’s a http:// link and then print it as

print "<a href='http://www.example.com'>http://www.example.com</a>";

I remember doing something like this before however, it was not fool proof it kept breaking for complex links.

Another good idea would be if you have a link such as

http://example.com/test.php?val1=bla&val2blablabla%20bla%20bla.bl

fix it so it does

print "<a href='http://example.com/test.php?val1=bla&val2=bla%20bla%20bla.bla'>";
print "http://example.com/test.php";
print "</a>";

This one is just an after thought.. stackoverflow could also probably use this as well :D

Any Ideas

Answer 1

This worked for me (turned one of the answers into a PHP function)

function make_urls_from_text ($text){
   return preg_replace('/(http[s]{0,1}\:\/\/\S{4,})\s{0,}/ims', '<a href="$1" target="_blank">$1 </a>', $text);
}

Answer 2

If you want to trust the IANA you can get your current list of offcially supported TLDs in use there like:

  $validTLDs = 
explode("\n", file_get_contents('http://data.iana.org/TLD/tlds-alpha-by-domain.txt')); //get the official list of valid tlds
  array_shift($validTLDs); //throw away first line containing meta data
  array_pop($validTLDs); //throw away last element which is empty

Makes Søren Løvborg's solution #2 a bit less verbose and spares you the hassle of updating the list, nowadays new tlds are thrown out so carelessly ;)

Answer 3

Let's look at the requirements. You have some user-supplied plain text, which you want to display with hyperlinked URLs.

1. The "http://" protocol prefix should be optional.
2. Both domains and IP addresses should be accepted.
3. Any valid top-level domain should be accepted, e.g. .aero and .xn--jxalpdlp.
4. Port numbers should be allowed.
5. URLs must be allowed in normal sentence contexts. For instance, in "Visit stackoverflow.com.", the final period is not part of the URL.
6. You probably want to allow "https://" URLs as well, and perhaps others as well.
7. As always when displaying user supplied text in HTML, you want to prevent cross-site scripting (XSS). Also, you'll want ampersands in URLs to be correctly escaped as &.
8. You probably don't need support for IPv6 addresses.
9. Edit: As noted in the comments, support for email-adresses is definitely a plus.
10. Edit: Only plain text input is to be supported – HTML tags in the input should not be honoured. (The Bitbucket version supports HTML input.)

Edit: Check out Bitbucket for the latest version, with support for email addresses, authenticated URLs, URLs in quotes and parentheses, HTML input, as well as an updated TLD list.

Please report bugs and enhancement requests using the Bitbucket issue tracker. They're easier to keep track of that way (and don't clutter the comment area).

Here's my take:

<?php
$text = <<<EOD
Here are some URLs:
stackoverflow.com/questions/1188129/pregreplace-to-detect-html-php
Here's the answer: http://www.google.com/search?rls=en&q=42&ie=utf-8&oe=utf-8&hl=en. What was the question?
A quick look at http://en.wikipedia.org/wiki/URI_scheme#Generic_syntax is helpful.
There is no place like 127.0.0.1! Except maybe http://news.bbc.co.uk/1/hi/england/surrey/8168892.stm?
Ports: 192.168.0.1:8080, https://example.net:1234/.
Beware of Greeks bringing internationalized top-level domains: xn--hxajbheg2az3al.xn--jxalpdlp.
And remember.Nobody is perfect.

<script>alert('Remember kids: Say no to XSS-attacks! Always HTML escape untrusted input!');</script>
EOD;

$rexProtocol = '(https?://)?';
$rexDomain   = '((?:[-a-zA-Z0-9]{1,63}\.)+[-a-zA-Z0-9]{2,63}|(?:[0-9]{1,3}\.){3}[0-9]{1,3})';
$rexPort     = '(:[0-9]{1,5})?';
$rexPath     = '(/[!$-/0-9:;=@_\':;!a-zA-Z\x7f-\xff]*?)?';
$rexQuery    = '(\?[!$-/0-9:;=@_\':;!a-zA-Z\x7f-\xff]+?)?';
$rexFragment = '(#[!$-/0-9:;=@_\':;!a-zA-Z\x7f-\xff]+?)?';

// Solution 1:

function callback($match)
{
    // Prepend http:// if no protocol specified
    $completeUrl = $match[1] ? $match[0] : "http://{$match[0]}";

    return '<a href="' . $completeUrl . '">'
        . $match[2] . $match[3] . $match[4] . '</a>';
}

print "<pre>";
print preg_replace_callback("&\\b$rexProtocol$rexDomain$rexPort$rexPath$rexQuery$rexFragment(?=[?.!,;:\"]?(\s|$))&",
    'callback', htmlspecialchars($text));
print "</pre>";

• To properly escape < and & characters, I throw the whole text through htmlspecialchars before processing. This is not ideal, as the html escaping can cause misdetection of URL boundaries.
• As demonstrated by the "And remember.Nobody is perfect." line (in which remember.Nobody is treated as an URL, because of the missing space), further checking on valid top-level domains might be in order.

Edit: The following code fixes the above two problems, but is quite a bit more verbose since I'm more or less re-implementing preg_replace_callback using preg_match.

// Solution 2:

$validTlds = array_fill_keys(explode(" ", ".aero .asia .biz .cat .com .coop .edu .gov .info .int .jobs .mil .mobi .museum .name .net .org .pro .tel .travel .ac .ad .ae .af .ag .ai .al .am .an .ao .aq .ar .as .at .au .aw .ax .az .ba .bb .bd .be .bf .bg .bh .bi .bj .bm .bn .bo .br .bs .bt .bv .bw .by .bz .ca .cc .cd .cf .cg .ch .ci .ck .cl .cm .cn .co .cr .cu .cv .cx .cy .cz .de .dj .dk .dm .do .dz .ec .ee .eg .er .es .et .eu .fi .fj .fk .fm .fo .fr .ga .gb .gd .ge .gf .gg .gh .gi .gl .gm .gn .gp .gq .gr .gs .gt .gu .gw .gy .hk .hm .hn .hr .ht .hu .id .ie .il .im .in .io .iq .ir .is .it .je .jm .jo .jp .ke .kg .kh .ki .km .kn .kp .kr .kw .ky .kz .la .lb .lc .li .lk .lr .ls .lt .lu .lv .ly .ma .mc .md .me .mg .mh .mk .ml .mm .mn .mo .mp .mq .mr .ms .mt .mu .mv .mw .mx .my .mz .na .nc .ne .nf .ng .ni .nl .no .np .nr .nu .nz .om .pa .pe .pf .pg .ph .pk .pl .pm .pn .pr .ps .pt .pw .py .qa .re .ro .rs .ru .rw .sa .sb .sc .sd .se .sg .sh .si .sj .sk .sl .sm .sn .so .sr .st .su .sv .sy .sz .tc .td .tf .tg .th .tj .tk .tl .tm .tn .to .tp .tr .tt .tv .tw .tz .ua .ug .uk .us .uy .uz .va .vc .ve .vg .vi .vn .vu .wf .ws .ye .yt .yu .za .zm .zw .xn--0zwm56d .xn--11b5bs3a9aj6g .xn--80akhbyknj4f .xn--9t4b11yi5a .xn--deba0ad .xn--g6w251d .xn--hgbk6aj7f53bba .xn--hlcj6aya9esc7a .xn--jxalpdlp .xn--kgbechtv .xn--zckzah .arpa"), true);

$position = 0;
while (preg_match("{\\b$rexProtocol$rexDomain$rexPort$rexPath$rexQuery$rexFragment(?=[?.!,;:\"]?(\s|$))}", $text, &$match, PREG_OFFSET_CAPTURE, $position))
{
    list($url, $urlPosition) = $match[0];

    // Print the text leading up to the URL.
    print(htmlspecialchars(substr($text, $position, $urlPosition - $position)));

    $domain = $match[2][0];
    $port   = $match[3][0];
    $path   = $match[4][0];

    // Check if the TLD is valid - or that $domain is an IP address.
    $tld = strtolower(strrchr($domain, '.'));
    if (preg_match('{\.[0-9]{1,3}}', $tld) || isset($validTlds[$tld]))
    {
        // Prepend http:// if no protocol specified
        $completeUrl = $match[1][0] ? $url : "http://$url";

        // Print the hyperlink.
        printf('<a href="%s">%s</a>', htmlspecialchars($completeUrl), htmlspecialchars("$domain$port$path"));
    }
    else
    {
        // Not a valid URL.
        print(htmlspecialchars($url));
    }

    // Continue text parsing from after the URL.
    $position = $urlPosition + strlen($url);
}

// Print the remainder of the text.
print(htmlspecialchars(substr($text, $position)));

Answer 4

Here is the code using Regular Expressions in function

<?php
//Function definations
function MakeUrls($str)
{
$find=array('`((?:https?|ftp)://\S+[[:alnum:]]/?)`si','`((?<!//)(www\.\S+[[:alnum:]]/?))`si');

$replace=array('<a href="$1" target="_blank">$1</a>', '<a href="http://$1" target="_blank">$1</a>');

return preg_replace($find,$replace,$str);
}
//Function testing
$str="www.cloudlibz.com";
$str=MakeUrls($str);
echo $str;
?>

Answer 5

This RegEx should match any link except for these new 3+ character toplevel domains...

{
  \\b
  # Match the leading part (proto://hostname, or just hostname)
  (
    # http://, or https:// leading part
    (https?)://[-\\w]+(\\.\\w[-\\w]*)+
  |
    # or, try to find a hostname with more specific sub-expression
    (?i: [a-z0-9] (?:[-a-z0-9]*[a-z0-9])? \\. )+ # sub domains
    # Now ending .com, etc. For these, require lowercase
    (?-i: com\\b
        | edu\\b
        | biz\\b
        | gov\\b
        | in(?:t|fo)\\b # .int or .info
        | mil\\b
        | net\\b
        | org\\b
        | [a-z][a-z]\\.[a-z][a-z]\\b # two-letter country code
    )
  )

  # Allow an optional port number
  ( : \\d+ )?

  # The rest of the URL is optional, and begins with /
  (
    /
    # The rest are heuristics for what seems to work well
    [^.!,?;"\\'()\[\]\{\}\s\x7F-\\xFF]*
    (
      [.!,?]+ [^.!,?;"\\'()\\[\\]\{\\}\s\\x7F-\\xFF]+
    )*
  )?
}ix

It's not written by me, I'm not quite sure where I got it from, sorry that I can give no credit...

Answer 6

This should get your twitter handle without touching on your email /(?<=^|(?<=[^a-zA-Z0-9-.]))@([A-Za-z]+[A-Za-z0-9]+)/i