<?php
$summary = explode($textarea,' '); //split user input in words
echo $summary [0], ' ',$summary [1], ' ',$summary [2]; //print first 3 words
echo '<br>'; //newline
echo $summary [3], ' ',$summary [4]; //print 2 more words
echo '<br>'; //newline
echo $summary [5], ' ',$summary [6]; //print 2 more words
echo '...'; //dots
?>
Это может быть:
<?php
$summary = explode($textarea,' '); //split user input in words
echo $summary [0], ' ',$summary [1], ' ',$summary [2],'<br>',$summary [3], ' ',$summary [4],'<br>', $summary [5], ' ',$summary [6],'...';
?>