preg_match_all 和 foreach 只替换最后一个匹配

Question

I have the following code, which should make plain text links clickable. However, if there are several links, it only replaces the last one.

Code:

$nc = preg_match_all('#<pre[\s\S]*</pre>#U', $postbits, $matches_code); 
foreach($matches_code[0] AS $match_code) 
{
    $match = null;
    $matches = null;
    $url_regex = '#https?://(\w*:\w*@)?[-\w.]+(:\d+)?(/([\w/_.]*(\?\S+)?)?)?[^<\.,:;"\'\s]+#'; 
    $n = preg_match_all($url_regex, $match_code, $matches);
    foreach($matches[0] AS $match)
    {
        $html_url = '<a href="' . $match . '" target="_blank">' . $match . '</a>';
        $match_string = str_replace($match, $html_url, $match_code);
    }
    $postbits = str_replace($match_code, $match_string, $postbits); 
}

Result:

http://www.google.com

http://www.yahoo.com

http://www.microsoft.com/ <-- only this one is clickable

Expected result:

http://www.google.com

http://www.microsoft.com/

Where is my error?

Answer 1

if there are several links it only replaces the last one

Where is my error?

Actually, it's replacing all 3 links, but it replaces the original string each time.

foreach($matches[0] AS $match)
{
    $html_url = '<a href="' . $match . '" target="_blank">' . $match . '</a>';
    $match_string = str_replace($match, $html_url, $match_code);
}

The loop is executed 3 times, each time it replaces 1 link in $match_code and assigns the result to $match_string . On the first iteration, $match_string is assigned the result with a clickable google.com . On the second iteration, $match_string is assigned with a clickable yahoo.com . However, you've just replaced the original string, so google.com is not clickable now. That's why you only get your last link as a result.

---

There are a couple of things you may also want to correct in your code:

1. The regex #<pre[\\s\\S]*</pre>#U is better constructed as #<pre.*</pre>#Us . The class [\\s\\S]* is normally used in JavaScript, where there is no s flag to allow dots matching newlines.
2. I don't get why you're using that pattern to match URLs. I think you could simply use https?://\\S+ . I'll also link you to some alternatives here .
3. You're using 2 preg_match_all() calls and 1 str_replace() call for the same text, where you could wrap it up in 1 preg_replace() .

Code

$postbits = "
<pre>
http://www.google.com

http://w...content-available-to-author-only...o.com

http://www.microsoft.com/ <-- only this one clickable
</pre>";


$regex = '#\G((?:(?!\A)|.*<pre)(?:(?!</pre>).)*)(https?://\S+?)#isU';
$repl = '\1<a href="\2" target="_blank">\2</a>';

$postbits = preg_replace( $regex, $repl, $postbits);

ideone demo

Regex

• \\G Always from the first matching position in the subject.
• Group 1
  • (?:(?!\\A)|.*<pre) Matches the first <pre tag from the beggining of the string, or allows to get the next <pre tag if no more URLs found in this tag.
  • (?:(?!</pre>).)*) Consumes any chars inside a <pre> tag.
• Group 2
  • (https?://\\S+?) Matches 1 URL.