I have a script (I think I found it here some time ago) that checks for existance of a specific word, if found, it changes it to a hyperlink still with the same word.

I would like it to only change the first occurance of the word though, currently it changes every occurance.

$sql="select * from table where num='$num'";
$result = mysql_query($sql, $dblink) or die("System down");
$pairs = array(

'word1' => '<a href="http://www.example.com/">word1</a>',
'word2' => '<a href="http://www.example2.com/">word2</a>',

);

while ($newArray = mysql_fetch_array($result)){
$num = $newArray['num'];
$title = $newArray['title'];
$text = str_replace(array_keys($pairs), array_values($pairs), $newArray['text']);
}

How should I go about it? thanks in advance