preg_replace shortcode

Question

Hi I have a little plugin system, I use this shortcode for example: {google}stackoverflow{/google}

I want it to replace that part with a link to the google search link, in this case: stackoverflow

How should I do this? I have this but it doesn't work:

preg_replace('#{google}([^{]+){/google}#i', '<a href="http://www.google.com?s=$1">$1</a>', $content);

What about it doesn't work? The regex doesn't return matches? There's an error message? If so, what's the error message? — Matt
– Matt, Commented Aug 22, 2012 at 19:46
Be aware though that this piece of code is highly vulnerable to XSS in case it may be used by not only "trustworthy" users. — Daniel M
– Daniel M, Commented Aug 22, 2012 at 19:48

KRyan · Accepted Answer · 2012-08-22 19:46:18Z

1

You need to escape the curly braces, i.e. use \{ and \}.

preg_replace('#\{google\}([^{]+)\{/google\}#i', '<a href="http://www.google.com?s=$1">$1</a>', $content);

answered Aug 22, 2012 at 19:46

KRyan

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KRyan Over a year ago

@Matt: I did, but I'm concerned that the URL will still need things like ' ' (backticks don't work?) swapped with + and ' replaced with %27: I'm not really certain the best way to do those. Not with regex, I'm certain.

FrankieTheKneeMan · Accepted Answer · 2012-08-22 19:46:56Z

1

The key here is to use a non-greedy operator, and escape everything.

preg_replace('#\{google\}(.*?)\{/google\}#i','<a href="http://www.google.com?s=$1">$1</a>', $content);

answered Aug 22, 2012 at 19:46

FrankieTheKneeMan

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2 Comments

FrankieTheKneeMan Over a year ago

@Matt since when? What's invalid about it?

Matt Over a year ago

Your curly brackets weren't escaped when I wrote my initial comment.

Matt · Accepted Answer · 2012-08-22 19:47:22Z

1

Your regex isn't valid. Try this:

preg_replace('#\{google\}[^\{]+\{/google\}#i', '<a href="http://www.google.com?s=$1">$1</a>', $content);

answered Aug 22, 2012 at 19:47

Matt

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chrisboustead · Accepted Answer · 2012-08-22 19:47:59Z

-1

preg_replace('#{google}([^{]+){\/google}#i', '<a href="http://www.google.com?s=$1">$1</a>', $content);

answered Aug 22, 2012 at 19:47

chrisboustead

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4 Comments

Matt Over a year ago

This is not a valid regex. The problem isn't the slash. OP uses # as the delimiter, so / doesn't need to be escaped. I'll remove my -1 if you can figure out which characters do need to be escaped.

chrisboustead Over a year ago

Got me, didn't notice the '#' rather than '/', but how is it not valid? Taking a closer look, OP's original example works, so does mine for that example. Curly brackets would need to be replaced in certain scenarios, most obviously if he was using one for a delimiter or using them after a pattern in the right format. Curious to see if OP was trying to match a different subject. cdbconcepts.com/dev/reg.php

Matt Over a year ago

Curly braces are reserved characters. They must be escaped.

chrisboustead Over a year ago

@Matt I agree they are reserved in certain situations, but for PCRE syntax do not need to be escaped unless attempting to match something in valid form. i.e. if you want to match subject a{,5} you must escape them a\{,5\}. However if you are matching alpha characters a{g} no need to escape. Also if your pattern used them as delimiters {test{curly{i you'd need to escape the one in the pattern.

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