PHP study notes: Enter a sentence and output the words in reverse order

<?php
/**
 * Created by PhpStorm.
 * User: Administrator
 * Date: 2016/9/25 0025
 * Time: 22:29
 */
//需要被倒序的字符串
$str="I am a handsome boy.";
$str_len=strlen($str);
//echo $str_len;输出结果为20，确认没问题。
//截取.号之前的字符substr(string,start,length)
$str=substr($str,0,$str_len-1);
//echo $str;得出I am a handsome boy，语句没问题
//转为数组
$str_arr=explode(&#39; &#39;,$str);
//var_dump($str_arr);结果无误
//倒序接收
$str_str_new=array_reverse($str_arr);
//数组转为字符串
$str_str_new_str=implode(&#39; &#39;,$str_str_new);
echo &#39;转换前：&#39;.$str."<br/>".&#39;转换后：&#39;.$str_str_new_str.&#39;.&#39;;

<span   style="max-width:90%"><?php
//需要被倒序的字符串
$str="I am a handsome boy.";</span><br><span style="font-size: 18px;">
$str_len=strlen($str);</span><br><span style="font-size: 18px;">
$str=substr($str,0,$str_len-1);</span><br><span style="font-size: 18px;">
$str_arr=explode(&#39; &#39;,$str);
 
$str_str_new=array_reverse($str_arr);
 
$str_str_new_str=implode(&#39; &#39;,$str_str_new);</span><br><span style="font-size: 18px;">
echo &#39;转换前：&#39;.$str."<br/>".&#39;转换后：&#39;.$str_str_new_str.&#39;.&#39;;
?>
</span>