php iconv() : Detected an illegal character in input string

php iconv() : Detected an illegal character in input string_php技巧_脚本之家 https://www.jb51.net/article/25528.htm

<?php
/* 转换内部编码为 SJIS */
$str = mb_convert_encoding($str, "SJIS");

/* 将 EUC-JP 转换成 UTF-7 */
$str = mb_convert_encoding($str, "UTF-7", "EUC-JP");

/* 从 JIS, eucjp-win, sjis-win 中自动检测编码，并转换 str 到 UCS-2LE */
$str = mb_convert_encoding($str, "UCS-2LE", "JIS, eucjp-win, sjis-win");

/* "auto" 扩展成 "ASCII,JIS,UTF-8,EUC-JP,SJIS" */
$str = mb_convert_encoding($str, "EUC-JP", "auto");
?>