PHP之mb_check_encoding使用

摘要：检查字符串在指定的编码里是否有效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。要检查的字节流。成功时返回，或者在失败时返回。输出空输出编码的字符串设置文件编码为博客园和。

(PHP 4 >= 4.4.3, PHP 5 >= 5.1.3, PHP 7)
mb_check_encoding — Check if the string is valid for the specified encoding
mb_check_encoding — 检查字符串在指定的编码里是否有效

bool mb_check_encoding ([ string $var = NULL [, string $encoding = mb_internal_encoding() ]] )
// Checks if the specified byte stream is valid for the specified encoding. 
// It is useful to prevent so-called "Invalid Encoding Attack".

// 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）”。

The byte stream to check. If it is omitted, this function checks all the input from the beginning of the request.

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。

The expected encoding.

期望的编码。

Returns TRUE on success or FALSE on failure.

成功时返回 TRUE， 或者在失败时返回 FALSE。

 设置文件编码为gbk*/
$str = "博客园和github。";
echo mb_check_encoding( $str, "utf-8" ) . PHP_EOL;  //输出空
echo mb_check_encoding( $str, "gbk" ) . PHP_EOL; //输出1

/**utf-8编码的字符串  --> 设置文件编码为utf-8*/
$str = "博客园和github。";
echo mb_check_encoding( $str, "utf-8" ) . PHP_EOL;  //1
echo mb_check_encoding( $str, "gbk" ) . PHP_EOL; //输出空

$utf8Str = "我abc是谁.";
echo mb_check_encoding( $utf8Str, "utf-8" ) . PHP_EOL;  //输出1
//如果有中文标点符号则为空！！！
echo mb_check_encoding( $utf8Str, "gbk" ) . PHP_EOL; //输出1

/**自定义检测字符串编码是否为utf-8*/
function is_utf8( $str ) {
    return (bool) preg_match( "//u", serialize($str) );
}

echo "hello 中国!" .is_utf8( "hello 中国!" ) . PHP_EOL; //1

function check_utf8( $str ) {
    $len = strlen( $str );
    for ( $i = 0; $i < $len; $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 < 128 || $b > 191 ) {
                    return false;
                }
                $bytes --;
            }
        }
    }
    
    return true;
} // end of check_utf8

echo check_utf8("hello 中国").PHP_EOL; // 1
echo check_utf8( "x00xE3").PHP_EOL;  //空

/** check a strings encoded value */
function checkEncoding( $string, $string_encoding ) {
    $fs = $string_encoding == "UTF-8" ? "UTF-32" : $string_encoding;
    $ts = $string_encoding == "UTF-32" ? "UTF-8" : $string_encoding;
    
    return $string === mb_convert_encoding( mb_convert_encoding( $string, $fs, $ts ), $ts, $fs );
}

/* test 1 variables */
$string   = "x00x81";
$encoding = "Shift_JIS";

/* test 1 mb_check_encoding (test for bad byte stream) */
if ( true === mb_check_encoding( $string, $encoding ) ) {
    echo "valid (" . $encoding . ") encoded byte stream!" . PHP_EOL;
} else {
    echo "invalid (" . $encoding . ") encoded byte stream!" . PHP_EOL;
}

/* test 1 checkEncoding (test for bad byte sequence(s)) */
if ( true === checkEncoding( $string, $encoding ) ) {
    echo "valid (" . $encoding . ") encoded byte sequence!" . PHP_EOL;
} else {
    echo "invalid (" . $encoding . ") encoded byte sequence!" . PHP_EOL;
}

/* test 2 */
/* test 2 variables */
$string   = "x00xE3";
$encoding = "UTF-8";
/* test 2 mb_check_encoding (test for bad byte stream) */
if ( true === mb_check_encoding( $string, $encoding ) ) {
    echo "valid (" . $encoding . ") encoded byte stream!" . PHP_EOL;
} else {
    echo "invalid (" . $encoding . ") encoded byte stream!" . PHP_EOL;
}

/* test 2 checkEncoding (test for bad byte sequence(s)) */
if ( true === checkEncoding( $string, $encoding ) ) {
    echo "valid (" . $encoding . ") encoded byte sequence!" . PHP_EOL;
} else {
    echo "invalid (" . $encoding . ") encoded byte sequence!" . PHP_EOL;
}

http://php.net/manual/zh/func...