Question

I would like to be able to switch this…

My sample [a id='keyword' href='someURLkeyword'] test keyword test[/a] link this keyword here.

To…

My sample [a id='keyword' href='someURLkeyword'] test keyword test[/a] link this [a href='url']keyword[/a] here.

I can’t simply replace all instances of ‘keyword’ because some are used in or within an existing anchor tag.

Note: Using PHP5 preg_replace on Linux.

Answer 1

Using regular expressions may not be the best way to solve this problem, but here is a quick solution:

function link_keywords($str, $keyword, $url) {     $keyword = preg_quote($keyword, '/');     $url = htmlspecialchars($url);      // Use split the string on all <a> tags, keeping the matched delimiters:     $split_str = preg_split('#(<a\s.*?</a>)#i', $str, -1, PREG_SPLIT_DELIM_CAPTURE);      // loop through the results and process the sections between <a> tags     $result = '';     foreach ($split_str as $sub_str) {         if (preg_match('#^<a\s.*?</a>$#i', $sub_str)) {             $result .= $sub_str;         } else {             // split on all remaining tags             $split_sub_str = preg_split('/(<.+?>)/', $sub_str, -1, PREG_SPLIT_DELIM_CAPTURE);             foreach ($split_sub_str as $sub_sub_str) {                 if (preg_match('/^<.+>$/', $sub_sub_str)) {                     $result .= $sub_sub_str;                 } else {                     $result .= preg_replace('/'.$keyword.'/', '<a href=''.$url.''>$0</a>', $sub_sub_str);                 }             }         }     }     return $result; } 

The general idea is to split the string into links and everything else. Then split everything outside of a link tag into tags and plain text and insert links into the plain text. That will prevent [p class=’keyword’] from being expanded to [p class='[a href=’url’]keyword[/a]’].

Again, I would try to find a simpler solution that does not involve regular expressions.