PHP string functions (6): search and replace

* 1.strpos($str1,$str2, $offset) finds the position where $str1 first appears in $str1

* 2.strstr($str1, $str2), if $str2 is The substring of $str1, returns the substring, otherwise returns false

* If it is determined that $str2 is the substring of $str1, it is recommended to use strpos(), which is faster

* 3.str_replace ($str1, $str2, $str3, $num): substring replacement, $num is the number of replacements

* 4.substr_replace($str1,$str2,$str3,$start, $length): Replace the substring of the string

$str = 'www.php.cn';

//1.strpos($str,$needle, $offset)Find the first occurrence of the string

echo strpos($str, &#39;p&#39;),&#39;<br>&#39;; //默认从头开始查找
echo strpos($str, &#39;p&#39;, 5),&#39;<br>&#39;; //从索引5开始查找

//2.strstr($str1 , $str2), if $str2 is a substring of $str1, return the substring, otherwise return false

echo strstr($str, &#39;php&#39;),&#39;<br>&#39;;  //返回子串及后面部分
echo strstr($str, &#39;php&#39;, true),&#39;<br>&#39;; //参数true,会返回子串前面部分
echo &#39;<hr>&#39;;

//3.str_replace($str1, $str2, $str3, $num): substring Replace,

echo str_replace(&#39;www&#39;,&#39;http://www&#39;,$str), &#39;<br>&#39;;
echo &#39;<hr>&#39;;

//4.substr_replace($str1,$str2,$str3,$start, $length): Replace the substring of the string

//In $str, The 2 characters starting from the 5th index position are replaced with 'pppph'

echo substr_replace($str,'pppph', 5, 2);