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up vote 0 down vote favorite

My understanding of Regex isn't great and I need to adapt my working JS code to PHP.

This is one of the run-throughs in JavaScript (it finds hashtags and makes HTML anchor tags out of them):

exp = /(^|\s)#(\w+)/g;
messagetext = messagetext.replace(exp, "$1<a class='myHashtag' href='http://search.twitter.com/search?q=%23$2' target='_blank'>#$2</a>");

How would this be done in PHP?

share|improve this question
5  
using preg_replace(), for starters – Wiseguy Jun 8 '13 at 2:55
    
The documentation is quite a helpful resource, a Google search is all it takes: php.net/manual/en/function.preg-replace.php – Qantas 94 Heavy Jun 8 '13 at 2:56
up vote 3 down vote

You can do it like this:

$messagetext = preg_replace('~^\h*+#\K\w++~m',
  '<a class="myHashtag" '
 .'href="http://search.twitter.com/search?q=%23$0" target="_blank">#$0</a>',
  $messagetext);

pattern detail:

^       # line's begining
\h*+    # horizontal space (ie space or tab), zero or more times (possessive)
#       # literal #
\K      # forgets all the begining!
\w++    # [a-zA-Z0-9_] one or more times (possessive)

Delimiters are ~ but you can choose other characters.

I use the multiline mode (m modifier), thus ^ stands for line's begining.

(possessive) indicates to the regex engine that it don't need to backtrack by adding a + after a quantifier. The subpattern becomes then more efficient.

share|improve this answer
    
Awesome, thank you! – tylerl Jun 8 '13 at 3:13
    
Actually, is it possible to do this using my original regexp? My expression didn't include the #, which was important. I could run another function to remove the # afterwards, but I'd like to avoid that... – tylerl Jun 8 '13 at 6:55
    
@tylerl, you can use exactly the same regex in PHP as your JS regex without modifications. That you even ask this without trying... See comments on your question. – Qtax Jun 8 '13 at 7:43
    
@tyler: as Qtax say, you can use your regex and replacement, but note that my expression don't include the # too cause i use the \K trick. – Casimir et Hippolyte Jun 8 '13 at 12:28
    
Ahhh! I see now, I guess (late!) last night when I tried it I gave up with my regexp when it was producing completely blank text - I tried it again and removed the g at the end... Thanks for the help! – tylerl Jun 8 '13 at 16:00

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