截取UTF-8编码下字符串的函数

/**
* 截取UTF-8编码下字符串的函数
*
* @param string str被截取的字符串∗@paramintlength 截取的长度
* @param bool append是否附加省略号∗∗@returnstring∗/functionsubstr(str, length=0,append = true)
{
str=trim(str);
strlength=strlen(str);

if ($length == 0 || $length >= $strlength){    return $str;}elseif ($length < 0){    $length = $strlength + $length;    if ($length < 0)    {        $length = $strlength;    }}if (function_exists('mb_substr')){    $newstr = mb_substr($str, 0, $length, 'utf-8');}elseif (function_exists('iconv_substr')){    $newstr = iconv_substr($str, 0, $length, utf-8);}else{    //$newstr = trim_right(substr($str, 0, $length));    $newstr = substr($str, 0, $length);}if ($append && $str != $newstr){    $newstr .= '...';}return $newstr;

}