How to filter invisible characters in php

php method to filter invisible characters: first create a PHP code sample file; then define a "filterNonPrintableChar" method; then implement filtering logic through isset, ord and other functions; finally output the filtering results through "var_dump" Can.

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php filter invisible characters

Coding knowledge

ASCII codes are reserved for standard symbols, numbers, English, etc. The value range is 0~127, and some are extended ASCII codes 128~255. When the operating system uses non-ASCII encoding (such as Chinese character encoding), extended ASCII code is generally used. It is agreed to use a coding range of 128 to 255 for 2 to 3 or even 4 consecutive bytes to encode Chinese characters.

So you can judge whether the ASCII code decimal value is greater than 127 to filter out Chinese characters.

php code

<?php
/**
 * @param $str
 * @return string
 * 过滤不可见字符，支持中文过滤
 * 0至31和127这33个编码是不可见的特殊字符（控制符）
 */
function filterNonPrintableChar($str)
{
    $i = 0;
    $newStr = &#39;&#39;;
    while (isset($str[$i])) {
        $char = $str[$i];
        $asc = ord($char);
        if ($asc > 31 && $asc < 127 || $asc > 127) {
            $newStr .= $char;
        }
        $i++;
    }
    return $newStr;
}
$str = chr(1) ."a3#2%1". chr(2) . chr(54) . "s哈哈ad~a好的s";
var_dump(filterNonPrintableChar($str));
$str = "“ASCII码为标准符号、数字、英文等进行了保留,取值范围是0～127,还有一部分作为扩展ASCII码128～255当操作系统采用非ASCII编码时(比如汉字编码),一般用扩展ASCII码来进行,约定用128～255范围的编码连续2～3甚至4个来进行...”";
var_dump(filterNonPrintableChar($str));

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