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'));
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;
}
}
{
$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;
}
}
