<?php
$str="i am a book\n\n\n\n\nmoth";
//去除所有的空格和换行符
echo preg_replace("/[\s]{2,}/","",$str).'<br>';
//去除多余的空格和换行符，只保留一个
echo preg_replace("/([\s]{2,})/","\\1",$str);
//去除多余的空格或换行 $text = preg_replace("/(\r\n|\n|\r|\t)/i", '', $text);
$lastSeveralLineContentsArr = preg_replace("/([ |\t]{0,}[\n]{1,}){2,}/","",$lastSeveralLineContentsArr);//对Html里有连续的空行或tab给正则过滤掉>
?>