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Homephp教程php手册php使用mb_check_encoding检查字符串在指定的编码里是否有效

本文说的是PHP使用mb_check_encoding检查字符串在指定的编码里是否有效的实例

mb_check_encoding — 检查字符串在指定的编码里是否有效
PHP 版本要求: (PHP 4 >= 4.4.3, PHP 5 >= 5.1.3)
说明:bool mb_check_encoding ([ string $var = NULL [, string $encoding = mb_internal_encoding() ]] )
检查指定的字节流在指定的编码里是否有效。它能有效避免所谓的“无效编码攻击(Invalid Encoding Attack)”。
参数
var
要检查的字节流。如果省略了这个参数,此函数会检查所有来自最初请求所有的输入。
encoding
期望的编码。
返回值
成功时返回 TRUE, 或者在失败时返回 FALSE。
为了检查是否一个字符串编码正确在utf - 8中,我建议以下函数实现 mb_check_encoding():

复制代码 代码如下:


function check_utf8($str) {
    $len = strlen($str);
    for($i = 0; $i         $c = ord($str[$i]);
        if ($c > 128) {
            if (($c > 247)) return false;
            elseif ($c > 239) $bytes = 4;
            elseif ($c > 223) $bytes = 3;
            elseif ($c > 191) $bytes = 2;
            else return false;
            if (($i + $bytes) > $len) return false;
            while ($bytes > 1) {
                $i++;
                $b = ord($str[$i]);
                if ($b 191) return false;
                $bytes--;
            }
        }
    }
    return true;
} // end of check_utf8
?>

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