Regex to replace tags in a string in PHP

Question

I am using the PHP and Regex below to search through a huge string for

[LINK]www.anyurl.com[/LINK]

and replace it with:

<a href="http://www.anyurl.com">http://www.anyurl.com</a>

The http:// is prepended if http or ftp do not exist in front of the url already.

$re = '/\[LINK]((?:(?!(http|ftp)|\[\/LINK]).)*)\[\/LINK]/i'; 
$subst = '[LINK]http://$1[/LINK]'; 
$xtext = preg_replace($re, $subst, $xtext, 1);
$xtext = preg_replace("/(\[LINK\])(\S*)(\[\/LINK])/", "<a href=\"$2\" target='_blank'>$2</a>", $xtext);

My problem is it only appears to be working for the first match it comes to and not other [LINK]www.urls.com[/LINK] in the document. The document being $xtext

@developerwjk I am not parsing HTML tags. When did [LINK] [/LINK] become a HTML tag? — MikeC
– MikeC, Commented May 30, 2014 at 22:26
@MathewFoscarini I wouldn't mind but they could provide a solution rather than just saying what they say. The solution I have above is fast and works well but i need it to repeat. I expect those that attack don't actually understand what they are seeing. — MikeC
– MikeC, Commented May 30, 2014 at 22:30

MikeC · Accepted Answer · 2014-05-30 22:52:46Z

1

Whoops, I have just found my error and it is so simple. In my third line:

$xtext = preg_replace($re, $subst, $xtext, 1);

I have 1 at the end of the preg_replace i.e. replace once. This should be set to -1 or left blank to replace all.

answered May 30, 2014 at 22:52

MikeC

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Comments

developerwjk · Accepted Answer · 2014-05-30 23:08:16Z

0

I think your problem could be the greedyness of your first regex. As you prepend the http:// to your first found link, all other links will stay the same. So please try (note the additional questionmark in line one):

$re = '/\[LINK]((?:(?!(http|ftp)|\[\/LINK]).)*?)\[\/LINK]/i'; 
$subst = '[LINK]http://$1[/LINK]'; 
$xtext = preg_replace($re, $subst, $xtext);
$xtext = preg_replace("/(\[LINK\])(\S*)(\[\/LINK])/", "<a href=\"$2\" target='_blank'>$2</a>", $xtext);

edited May 30, 2014 at 23:08

developerwjk

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answered May 30, 2014 at 22:42

SomeoneYouDontKnow

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developerwjk · Accepted Answer · 2014-05-30 23:08:59Z

0

In the first expression the 1 needed to be removed, as you already figured out. Notice the second expression is the same as your second expression but with * replaced with +?, and the unnecessary capture groups around the tags removed. * doesn't stop at the first [\LINK] but at the last one, resulting in a link with display text like http://www.google.com[/LINK]\n[LINK]http://www.yahoo.com so +? is needed.

$xtext = '[LINK]www.google.com[/LINK]\n[LINK]www.yahoo.com[/LINK]';

$re = '/\[LINK]((?:(?!(http|ftp)|\[\/LINK]).)*)\[\/LINK]/i';
$subst = '[LINK]http://$1[/LINK]';
$xtext = preg_replace($re, $subst, $xtext, 1);

$xtext = preg_replace("/\[LINK\](\S+?)\[\/LINK]/", "<a href='$1' target='_blank'>$1</a>", $xtext);

edited May 30, 2014 at 23:08

answered May 30, 2014 at 22:50

developerwjk

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3 Comments

MikeC Over a year ago

You are not checking if the link has http or ftp prepended to it in the first place. Mine checks if the link is [LINK]www.example.com[/LINK] or [LINK]example.com[/LINK] and if it is the former prepends http:// to it.

MikeC Over a year ago

@developerwjk Your expression substituting my (\S*) for your (\S+?) takes 58 iterations while mine takes 32. I'll stick with mine. I don't see where you have rationalised the capture groups in your example??? Anyway I solved the issue, you started off abusive, have given me 2 incorrect answers so we will leave it there.

developerwjk Over a year ago

@MikeC, Abusive? I was explaining j_mcnally's comment.

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