php截取字符串之截取utf8或gbk编码的中英文字符串示例

微博的发言有字数限制,其计数方式是,中文算2个,英文算1个,全角字符算2个,半角字符算1个。
php中自带strlen是返回的字节数,对于utf8编码的中文返回时3个,不满足需求。
mb_strlen 可以根据字符集计算长度,比如utf8的中文计数为1,但这不符合微博字数限制需求,中文必须计算为2才可以。
google了下,找到一个discuz中截取各种编码字符的类,改造了下,已经测试通过.其中参数$charset 只支持gbk与utf-8。

代码如下:

$a = "s@@你好";
var_dump(strlen_weibo($a,'utf-8'));

结果输出为8,其中字母s计数为1,全角@计数为2,半角@计数为1,两个中文计数为4。源码如下:

代码如下:

function strlen_weibo($string, $charset='utf-8')
{
    $n = $count = 0;
    $length = strlen($string);
    if (strtolower($charset) == 'utf-8')
    {
        while ($n < $length)
        {
            $currentByte = ord($string[$n]);
            if ($currentByte == 9 ||
                $currentByte == 10 ||
                (32 <= $currentByte && $currentByte <= 126))
            {
                $n++;
                $count++;
            } elseif (194 <= $currentByte && $currentByte <= 223)
            {
                $n += 2;
                $count += 2;
            } elseif (224 <= $currentByte && $currentByte <= 239)
            {
                $n += 3;
                $count += 2;
            } elseif (240 <= $currentByte && $currentByte <= 247)
            {
                $n += 4;
                $count += 2;
            } elseif (248 <= $currentByte && $currentByte <= 251)
            {
                $n += 5;
                $count += 2;
            } elseif ($currentByte == 252 || $currentByte == 253)
            {
                $n += 6;
                $count += 2;
            } else
            {
                $n++;
                $count++;
            }
            if ($count >= $length)
            {
                break;
            }
        }
        return $count;
    } else
    {
        for ($i = 0; $i < $length; $i++)
        {
            if (ord($string[$i]) > 127)
            {
                $i++;
                $count++;
            }
            $count++;
        }
        return $count;
    }
}

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