Usage examples of common string processing functions in PHP [conversion, escaping, interception, comparison, search, reversal, cutting]

<?php
$s = "hello world";
//整理
echo &#39;trim(); ltrim(); rtrim()&#39;;
echo &#39;<br />&#39;;
echo &#39;长度为: &#39;.strlen($s);
echo &#39;<br />&#39;;
//大小写
echo &#39;首字母大写: &#39;.Ucfirst($s);
echo &#39;<br />&#39;;
echo &#39;每个单词首字母大写: &#39;.Ucwords($s);
echo &#39;<br />&#39;;
echo &#39;大写: &#39;. Strtoupper($s);
echo &#39;<br />&#39;;
echo &#39;小写: &#39;. Strtolower($s);
echo &#39;<br />&#39;;
// 转义字符串函数,存入数据库前使用
echo &#39;addslashes(); stripslashes();&#39;;
$s1 = &#39;"a"b&#39;;
echo &#39;<br />&#39;;
echo addslashes($s1);
echo &#39;<br />&#39;;
//截取
echo substr($s, 4, 4);
echo &#39;<br />&#39;;
$s2 = "hello world";
$s3 = "test";
//比较,相等返回0
echo strcmp($s, $s2) == 0 ? "相等":"不等";
echo &#39;<br />&#39;;
echo strcmp($s, $s3) == 0 ? "相等":"不等";
echo &#39;<br />&#39;;
//查找
echo strpos($s, &#39;o&#39;);
echo &#39;<br />&#39;;
echo strrpos($s, &#39;o&#39;);
//注意:如果查不到,则返回false == 0,所以要用"==="来检查if (XX === false);
echo &#39;<br />&#39;;
//反转
echo strrev($s);
echo &#39;<br />&#39;;
//切割
$arr = str_split($s);
$arr1 = str_split($s, 2);
$arr2 = explode(&#39; &#39;, $s);
var_dump($arr);
var_dump($arr1);
var_dump($arr2);
?>