TobyInkster.co.uk
18/07/2007: PHP Linkifier
Here’s a nifty bit of code I wrote a while back (utilising a function from PHP SmartyPants) that takes a bunch of HTML, searches it for some word or phrase that you specify, and turns all occurances of it into a link, unless it’s already a link!
<?php
// how many times do you want to allow the tokenizer to loop?
// The higher the value, the longer your system could churn
// given an infinite-loop bug (or really really really long text string).
define('MAX_TOKENIZER_LOOPS', 2000);
// print error on tokenizer loop problem?
define('ADVISE_TOKENIZER_FAILURE', FALSE);
// keys for $tokens hash
define('TOKENS_TYPE_TEXT', 'text');
define('TOKENS_TYPE_TAG', 'tag');
function _tokenize(&$str, &$tokens) {
#
# Parameter: Pointer to string containing HTML markup,
# pointer to array to store results.
#
# Output array contains tokens comprising the input
# string. Each token is either a tag (possibly with nested,
# tags contained therein, such as <a href="<MTFoo>">, or a
# run of text between tags. Each element of the array is a
# two-element array; the first is either 'tag' or 'text';
# the second is the actual value.
#
# Based on the _tokenize() subroutine from Brad Choate's MTRegex plugin.
# <http://www.bradchoate.com/past/mtregex.php>
$len = strlen($str);
$depth = 6;
$nested_tags = str_repeat('(?:<(?:[^<>]|', $depth);
$nested_tags = substr($nested_tags, 0, -1);
$nested_tags .= str_repeat(')*>)', $depth);
$match = "/(?s: <! ( -- .*? -- \s* )+ > ) |
(?s: <\? .*? \?> ) |
$nested_tags/x";
$last_tag_end = -1;
$loops = $offset = 0;
while (preg_match($match, substr($str, $offset), $hits, PREG_OFFSET_CAPTURE)) {
$extracted_tag = $hits[0][0]; // contains the full HTML tag
$tag_start = $offset + (int)$hits[0][1]; // position of captured in string
$offset = $tag_start + 1; // tells preg_match where to start on next iteration
// if this tag isn't next to the previous one, store the interstitial text
if ($tag_start > $last_tag_end) {
$tokens[] = array('type' => TOKENS_TYPE_TEXT,
'body' => substr($str, $last_tag_end+1, $tag_start-$last_tag_end-1));
}
$tokens[] = array('type' => TOKENS_TYPE_TAG,
'body' => $extracted_tag);
$last_tag_end = $tag_start + strlen($extracted_tag) - 1;
if ($loops++ > MAX_TOKENIZER_LOOPS) {
if (ADVISE_TOKENIZER_FAILURE) {
print "SmartyPants _tokenize failure.";
}
return;
}
}
// if text remains after the close of the last tag, grab it
if ($offset < $len) {
$tokens[] = array('type' => TOKENS_TYPE_TEXT,
'body' => substr($str, $last_tag_end + 1));
}
return;
}
function linkity ($string, $word, $link='', $casesensitive=FALSE)
{
if ($link=='')
$link = 'http://en.wikipedia.org/wiki/'.ucfirst($word);
$regexp = '#\b('.$word.')\b#'.($casesenitive?'':'i');
$inlink = FALSE;
$out = '';
$tokens = array();
_tokenize($string, $tokens);
foreach ($tokens as $t)
{
if ($t['type']==TOKENS_TYPE_TAG)
{
if (preg_match('#<a#i', $t['body']))
$inlink = TRUE;
elseif (preg_match('#</a#i', $t['body']))
$inlink = FALSE;
$out .= $t['body'];
}
else
{
if ($inlink)
$out .= $t['body'];
else
$out .= preg_replace($regexp,
"<a href=\"{$link}\">$1</a>",
$t['body']);
}
}
return $out;
}
$str = 'Let\'s go to <a href="my.htm">my car</a>. Tomorrow I\'ll have to buy
a new car because there is a problem with the carburettor.';
print "$str\n";
print linkity($str, 'car')."\n";
?>