经测试代码如下：
<?PHP
/**
* 按单词截取字符串
*
* @param
* @arrange (512.笔记) jb51.cc
**/
function limit_words($string,$word_limit)
{
$words = explode(" ",$string);
return implode(" ",array_splice($words,$word_limit));
}
# Example Usage
$content = "Lorem ipsum dolor sit amet,consectetur adipisicing elit,sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam,quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident,sunt in culpa qui officia deserunt mollit anim id est laborum.";
echo limit_words($content,20);
/*** 来自：编程之家 jb51.cc（jb51.cc） ***/
?>