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）”。

<?php/** * Created by PhpStorm. * User: zhangrongxiang * Date: 2018/1/27 * Time: 下午2:59 *//**纯数字和英文字母组合*/$utf8Str = "I have 4 books and 2 magazines to check out. ";echo ( mb_check_encoding( $utf8Str, ‘utf-8‘ ) ) . PHP_EOL; //输出1echo ( mb_check_encoding( $utf8Str, ‘gbk‘ ) ) . PHP_EOL; //输出1echo bin2hex( $utf8Str ) . PHP_EOL;//492068617665203420626f6f6b7320616e642032206d6167617a696e657320746f20636865636b206f75742e20$gbkStr = mb_convert_encoding( $utf8Str, ‘gbk‘, ‘utf-8‘ );echo bin2hex( $gbkStr ) . PHP_EOL;//492068617665203420626f6f6b7320616e642032206d6167617a696e657320746f20636865636b206f75742e20/**gbk编码的字符串 ?--> 设置文件编码为gbk*/$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; ?//1echo 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; //1function 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_utf8echo check_utf8("hello 中国").PHP_EOL; // 1echo check_utf8( "\x00\xE3").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 ??= "\x00\x81";$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 ??= "\x00\xE3";$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;}