multiple text replace inside a string, while keeping the selected variable - php

Question

I have a web script that creates a HTML page into a PHP string, then delivers it to the user. All of the pages are generated by index.php, with a unique url.
domain.host.com/index.php?loadpage=/BLAH
The homepage is static HTML, but every other page is dynamically generated into this PHP string. It may seem like im rambling, just trying to give as much info as possible. I have created a javascript code to modify the link url:
BLAH Link
This basically shows the nice neat link in the status bar, but the javascript sends it to the URL i want (I have no need to modify the url bar, as this is in an iframe)
These links are fine on the static page. But on the dynamically generated page thats in the PHP string is a little harder. I need to search through a string for every occurence of:
href="?loadpage=/ [WILDCARD] " title=
and replace it with:
href="http://domain.com/ [WILDCARD] " onclick="location.href='?loadpage=/ [WILDCARD] '; return false;" title=
This seems very complicated to me and I think it could be ereg / preg match / replace, but have no clue with regex.
In a short summary, I need some way of searching through a php string that contains the full page html, and replacing the first string with the second (on every occurance of a link with '?loadpage/'. But each link will have a different [WILDCARD] so i'm presuming, that the script will need to find every occurance, save the [WILDCARD] to a variable, then do the replace function, and insert the word its just saved as a variable from the first url.
EDIT.
Just to clarify what the original link looks like:
<a id="random" href="?loadpage=/BLAH" title="BLAH Title"></a>
this is why i am only searching from the href attribute.

Answer 1

You are right, what you need is a regex. (Your need for a wildcard replace is the clue). This answer is not supposed to be a complete solution, just give you an idea how regexes work. I will leave it to you to integrate this with php (try preg_match_all)
This is the pattern you want to match:
"\?loadpage=\/([^"]*)"
The \ is an escape for characters that have special meaing in regexes
So ignoring the escapes this is
"?loadpage=/ //the start of the string up to the wildcard part
() // capturing parentheses, indicating a part that
// you want to access in the replace string
[^"]* // any number of occurences of any character that is NOT doublequote
// ^ is the negation symbol
// * indicates "zero or more occurrences"
followed by...
" doublequote character
Now you need a replacement string ... for this you just need to know that your (capture parentheses) allow you to recall that part of the match. In most regex flavours your can capture these to a series numbered variables, usually represented as $1, $2, $3.. \1 \2 \3... In your case you only have one capture variable to deal with.
So you replacement string could look like
"http://domain.com/$1/" onclick="location.href='?loadpage=/$1'; return false"
In perl you would put the whole thing together like this:
$string =~ s|"\?loadpage=\/([^"]*)"|"http://domain.com/$1/" onclick=\"location.href='?loadpage=/$1'\; return false"|g;
Note that you don't need to escape your quotemarks. This may differ in php.
As you will see it easily gets very cryptic. regular-expressions.info is a useful online reference.
just so you know what you are looking at (you won't need to do this in php)...
=~ is the perl regex operator (you won't use this in php, take a look at the preg_match documentation)
then you have the form
s|match_pattern|replace_pattern|g;
where s indicates replacement (as opposed to simple matching)
g indicates global matching (otherwise process will stop on first match)
||| are the separators. Usually written /// but then you would have to escape all of your URL //s, which doubles the illegibility.
But this is now too much perl-specifc detail, read the php regex docs!