Detailed explanation of how PHP correctly calculates the length of Chinese strings

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Release: 2023-04-11 11:46:01
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In PHP programming, we often encounter scenarios where we need to calculate the length of a string. Generally, we are accustomed to using the strlen() function or mb_strlen() function to calculate the string length. However, when dealing with Chinese strings, we will find that there will be problems using the strlen() function, because Chinese characters do not calculate the length according to the general character calculation method. So how can we correctly calculate the length of Chinese strings in PHP? Let’s discuss related issues below.

1. How to calculate string length in PHP

In PHP, there are two ways to calculate string length, one is simple character counting, The other is calculated based on the actual character length. When calculating the length of a string, we will encounter two situations:

  1. ASCII characters: When calculating the length of ASCII characters, just use the strlen() function directly.
  2. Chinese characters: Chinese characters occupy two bytes in Unicode and two bytes or three bytes in GBK. When calculating the length of Chinese characters, it needs to be calculated according to the actual length of the characters.

2. Problems with misuse of strlen() function

strlen() function is a basic function in PHP used to calculate the length of a string. Can return the length of the specified string. However, when processing Chinese strings, there will be problems using the strlen() function, and the length calculation will be inaccurate. This is because PHP uses ASCII encoding by default, and for Unicode-encoded Chinese characters, one character is parsed into multiple bytes, resulting in an error when calculating the length.

For example, when using the strlen() function to calculate the length of the Chinese string "China", the result will return 6 instead of the expected 2. This is because the strlen() function will combine the Chinese characters "中" and "中" "Country" is parsed into 3 bytes respectively.

3. Methods to solve the problem

Since the strlen() function cannot calculate the length of Chinese characters normally, how should we calculate the length of Chinese characters? The following are three commonly used solutions:

  1. Use the mb_strlen() function

PHP provides the mb_strlen() function to solve the string length problem. The mb_strlen() function is a multi-byte string length function that returns the actual length of the string, including Chinese characters. When using the mb_strlen() function to calculate the length of a Chinese string, you need to pass in the second parameter to specify the character encoding, for example:

$str = '中国';
$len = mb_strlen($str, 'UTF-8'); // 返回 2
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This method is the most common and recommended, because the mb_strlen() function has a good readability and maintainability. Note that the mbstring extension must be installed before using the mb_strlen() function.

  1. Use iconv_strlen() function

iconv_strlen() function can be used to calculate the length of a string, and it can also correctly handle the length of Chinese strings. The iconv_strlen() function structure is similar to the strlen() function, except that when calculating the length, you need to pass in the second parameter to specify the character encoding, for example:

$str = '中国';
$len = iconv_strlen($str, 'UTF-8'); // 返回 2
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Similar to the mb_strlen() function, use the iconv_strlen() function You also need to confirm that the iconv extension is installed before.

  1. Calculate the number of bytes and divide it by 2 or 3

In addition to using PHP’s own functions, we can also calculate the bytes of Chinese characters To solve the length calculation problem, the method is as follows:

$str = '中国';
$len = ceil((strlen($str) - mb_strlen($str, "UTF-8")) / 2) + mb_strlen($str, "UTF-8");
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The above code first calculates the number of bytes of Chinese characters, then divides by the actual length of 2 or 3, and finally adds the length of English characters, you can get Correct Chinese string length.

4. Summary

In short, in PHP programming, the calculation of Chinese string length is quite special and requires our special attention. To avoid errors, we should choose an appropriate calculation method, such as using the mb_strlen() function or iconv_strlen() function, or calculating the length by counting the number of bytes and dividing it by 2 or 3. This can ensure the correctness of the Chinese character length and prevent calculation errors and data anomalies.

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