How to detect how many Chinese characters a string contains in php

Detection steps: 1. Use the preg_replace() function with regular expressions to filter strings and remove non-Chinese letters in the strings. The syntax is "preg_replace("/[^\x{4E00}-\x{ 9FFF}] /u",'', original string)" will return a string containing all Chinese letters; 2. Use the mb_strlen() function to calculate the length of the filtered string (the number of Chinese characters), the syntax "mb_strlen(filter string,"utf-8")".

The operating environment of this tutorial: Windows 7 system, PHP version 8.1, DELL G3 computer

In PHP, you can use the preg_replace() function and mb_strlen() function to detect how many Chinese characters a string has.

Implementation steps:

Step 1: Use the preg_replace() function with regular expressions to filter the string and remove the strings Non-Chinese letters

preg_replace() deletion principle: Use regular expressions to search for non-Chinese letters in the string and replace them with the empty character ''.

<?php
header("Content-type:text/html;charset=utf-8");
$str = "欢迎4546来到php这里。zblog,我的?#$%^天呀&())*(&^";
echo "原字符串：";
var_dump($str);
$pattern = "/[^\x{4E00}-\x{9FFF}]+/u";
echo "过滤字符串后：";
$newStr=preg_replace($pattern,&#39;&#39;, $str);
var_dump($newStr);
?>

will return a string containing all Chinese letters

Step 2: Use the mb_strlen() function to calculate the length of the filtered string (Chinese Number of characters)

$len=mb_strlen($newStr,"utf-8");
echo "中文字符的个数：".$len;

Description:

preg_replace():

preg_replace() function can perform regular expression search and replacement. It is a powerful string replacement processing function. The syntax format of this function is as follows:

preg_replace($pattern, $replacement, $subject [, $limit = -1 [, &$count]])

The parameter description is as follows:

• $pattern: The pattern to be searched, which can be a string or an array of strings;
• $replacement: The string or array of strings used for replacement. If this argument is a string and $pattern is an array, then all patterns are replaced with this string. If $pattern and $replacement are both arrays, each $pattern is replaced with the corresponding element in $replacement. If there are fewer elements in $replacement than in $pattern, the extra $pattern is replaced with the empty string.
• $subject: The string or string array to be searched and replaced. If $subject is an array, the search and replacement will be performed on each element of $subject, and the return value will also be one array.
• $limit: Optional parameter, the maximum number of substitutions per pattern on each $subject. Default is -1 (infinite).
• $count: Optional parameter, if specified, will be filled with the number of completed substitutions.

If $subject is an array, the preg_replace() function will return an array, otherwise it will return a string.

If the function preg_replace() finds a match, it will return the replaced $subject, otherwise it will return the unchanged $subject. Each parameter of the preg_replace() function (except the parameter $limit) can be an array. If the $pattern parameter and the $replacement parameter are both arrays, the function will process the keys in the order they appear in the array. If an error occurs, NULL is returned.

The parameter $replacement can contain back references \\n or $n, the latter is preferred syntactically. Each such reference will be replaced by the text captured by the nth capturing subgroup that was matched. n can be 0-99, with \\0 and $0 representing the complete pattern matching text.

The serial number counting method of capturing subgroups is: the left bracket representing the capturing subgroup is counted from left to right, starting from 1. If you want to use backslashes in $replacement, you must use 4 ("\\\\" because this is first a php string, and after escaping it is two, and then it is considered as a string after passing through the regular expression engine. an original backslash).

When working in replacement mode and the backreference needs to be followed by another number (for example: adding an original number immediately after a matching pattern), you cannot use the syntax \\1. Describes backreferences. For example, \\11 will make preg_replace() unable to understand whether you want a \\1 backreference followed by an original 1, or a \\11 backreference followed by nothing. The solution in this case is to use ${1}1. This creates a separate backreference for $1, a separate backreference for source 1.

When using the deprecated e modifier, this function will escape some characters (ie: ', ", \ and NULL) and then perform backreference replacement. When this is done please make sure to backreference After the reference is parsed, there are no syntax errors caused by single quotes or double quotes (for example: 'strlen(\'$1\') strlen("$2")'). Ensure that it conforms to PHP's string syntax and complies with eval syntax. Because in After completing the replacement, the engine will evaluate the resulting string as a php code using the eval method and use the return value as the final string participating in the replacement.

mb_strlen() function

mb_strlen()函数可以计算英文字符串、中文字符串或中英混合字符串的长度。

mb_strlen($str [, $encoding = mb_internal_encoding()])

• $str 为需要计算长度的字符串

• $encoding 是可选参数，为字符编码，如果省略则使用内部字符编码。

mb_strlen() 函数的返回值为具有 $encoding 编码的字符串 $str 所包含的字符数，如果 $encoding 无效则返回 false。

注意：在 mb_strlen() 函数中，无论是汉字，还是英文、数字、小数点、下划线和空格，都只占一个字符长度。

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