string mb_strstr ( 
 string $haystack , 
 string $needle [, 
 bool $before_needle = false [, 
 string $encoding =mb_internal_encoding() ]] 
 )

//mb_strstr() finds the first occurrence of needle in haystack and returns the portion of haystack. If needle is not found, it returns FALSE.
//mb_strstr() 查找了 needle 在 haystack 中首次的出現并返回 haystack 的一部分。 如果 needle 沒有找到，它將返回 FALSE。

?php
/**
 * Created by PhpStorm.
 * User: zhangrongxiang
 * Date: 2018/2/1
 * Time: 下午10:27
 */

//* * If set to true, it returns all of haystack from the beginning to the first occurrence of needle.
$strstr = mb_strstr( "hello china", "ll", true );
echo $strstr . PHP_EOL; //he

//* If set to false, it returns all of haystack from the first occurrence of needle to the end,
$strstr = mb_strstr( "hello china", "ll", false );
echo $strstr . PHP_EOL;//llo china

//hello china
echo mb_strstr( "hello china", "ll", true ) . mb_strstr( "hello china", "ll", false ) . PHP_EOL;

$strstr = mb_strstr( "hello China,hello PHP", "ll", true );
echo $strstr . PHP_EOL; //he

$strstr = mb_strstr( "hello China,hello PHP", "ll", false );
echo $strstr . PHP_EOL; //llo China,hello PHP

$strstr = mb_strstr( "PHP是世界上最好的語言😄", "最好", true );
echo $strstr.PHP_EOL; //PHP是世界上
$strstr = mb_strstr( "PHP是世界上最好的語言😄", "最好", false );
echo $strstr.PHP_EOL; //最好的語言😄