adding html links to a plain text

Consider I have a text of 开发者_StackOverflow社区300-400 words with some basic html. Example:

<p>text text word1 text text text filament text text text text text text text text</p>
<p>text text text text text text text text text text text text text text text</p>

And I have a list of keyphrase with their urls associated (about 1000 records)

word1 word2 => 'url'
house home  => 'url1'
flower filament => 'url2'

I need to place the url for the corrispondent word found in text. Example:

<p>text text <a href="url">word1</a> text [etc..]

I Know I can use a simple str_replace or preg_replace. But i dont' want to add to many links. Out of 300-400 words i don't want to put more than 5-6 links.

What can I Do?

use preg_replace() with the limit parameter, of course it will be the first X replacements, which may or may not be what you want

A small example that justs makes the first instance of each desired word bold. Should be easy to do other stuff with it as well. :)

<?
    // Your text
    $s = <<<YourText
<p>text text word1 text text text filament text text text text text text text text</p>
<p>text text text text text text text text text text text text text text text</p>
YourText;

    // The words you want to highlight
    $linkwords = array('text', 'word1', 'filament');

    // Split the string by using spaces
    $words = explode(' ', $s);
    print_r($words);

    // Words you have highlighted already.
    $done = array();

    // Loop through all words by reference
    foreach ($words as &$word)
    {
        // Highlight this word?
        if (array_search($word, $linkwords) !== false)
        {
            // Highlighted before?
            if (array_search($word, $done) === false)
            {
                // Remember it..
                $done[] = substr($word,0);
                // And highlight it.
                $word = '<b>'.$word.'</b>';
            }
        }
    }

    echo  implode(' ', $words);

First, from your question I figured that words/links ratio would be around 60. So, to give you an example, do the following:

define('WLRATIO', 60);

$mytext = "text text ..... ";
// Rough estimation of word count
$links = count(explode(' ', $mytext)) / WLRATIO;

$keywords = array(
    'foo' => 'url1',
    'bar' => 'url2'
    ...
);

$keys = array_keys($keys);

while ( $links-- ) {
    $n = rand(0, count($keys)-1);
    $mytext = preg_replace('/'+$keys[$n]+'/', '<a href="'+$keywords[$keys[$n]]+'">'+$keys[$n]+'</a>', $mytext, 1);
}

echo $mytext;