pattern matching help...finding A HREF tags

sneakyimp

hi:
I need to write a PHP function that will change all HTML links in a string ending in .html to end in .php. i.e., if the
the string had a link in it like this: <a href="link.html"> then the function would change that link to read: <a href="link.php">

my pattern matching skills are a little weak and i want to make sure the function can match tags like this <a
href = "blah blah"> but also <a href=foo.html> etc.

that is to say, quotes are optional, there may be other attributes in the tag (such as target, class or onclick tags) before or after the actual link. it also needs to handle arbitrary whitespace.

any help would be much appreciated!

sneakyimp

does this look allright?

function change_links_to_php($arg) {
   $find = "/(<a)([^>]+)(href=)(\")([^\"]*)(.htm\")([^>]*)(>)/i";
   $replace = "replaced\\1\\2\\3\\4\\5.php\"\\7\\8";
   return preg_replace($find,$replace, $arg);
}

Weedpacket

Originally posted by sneakyimp
does this look allright?

Well, the question is: does it work?🙂

In http://www.phpbuilder.com/board/showthread.php?s=&threadid=10223623 I give an expression for matching the href= attribute. It only does the matching; not the replacing, so it doesn't make any effort to capture all the other pieces of the tag (the .*? that aren't bracketed). But then you just need to bracket those! It tries to match "-, '- and  -quoted attributes, but it actually goes wonky on the last. It may be easier to do two searches - once with quotes, once without.

Consider looking at using preg_replace_callback() instead of preg_replace(). Then you don't have to do everything in the search expression or the replacement string, but instead write a function that will take the matched pieces, work them over (e.g., replace ".htm" and ".html" with ".php"), then put them together into a string that it returns for use as the replacement text.

sneakyimp

thanks for the response.

it does seem to work reasonably well...it only works where A tags are relatively well-behaved...i.e., only finds href=" (no spaces there, no single quotes, no A tags that don't use quotes). this is OK for now, I think.

i will check out the other thread. thanks weedpacket.