The key to getting string length in PHP is to select the appropriate function according to the character type. ① When processing English characters, strlen() can be used, which returns the number of bytes, which is the number of characters for single-byte characters; ② When involving Chinese or multi-byte characters, mb_strlen() should be used and UTF-8 encoding should be specified to accurately obtain the number of characters; ③ Pay attention to details such as mbstring extension, unified encoding format, and cleaning hidden characters in the server to ensure that the calculation results are correct.

Getting the length of a string in PHP is actually very simple, the key is to use the right function. If you are dealing with English characters, just use strlen() ; but if it involves Chinese or multi-byte characters, you have to change the method.

strlen() function: suitable for single-byte characters

This function is the most basic way to get the length of a string, which returns the number of bytes occupied by the string. For pure English characters, one letter accounts for 1 byte, so the result is the number of characters.

 echo strlen("hello"); // Output 5

However, be aware that if the string contains Chinese or other multi-byte characters, the result of strlen() is not the "number of characters" you want. For example, the following sentence:

 echo strlen("Hello world"); // Output 9

Because each Chinese character usually takes up 3 bytes under UTF-8, so here is a total of 2×3 5 = 11 bytes? Then why is the output 9? Don't worry, this question will be discussed later.

Use mb_strlen() to get the true number of characters

If you want to accurately count the number of characters in a mixed string in Chinese and English, you must use the mb_strlen() function and specify the encoding format as UTF-8 .

 echo mb_strlen("Hello world", 'UTF-8'); // Output 7

This will correctly identify that "Hello" is two characters and "world" is 5 English letters, totaling 7 characters.

The advantage of this function is that it supports multi-language and multi-byte encoding, which is especially suitable for functions such as username restriction and content interception. But the premise is that your server needs to install and enable mbstring extension, otherwise an error will be reported.

Pay attention to common misunderstandings and details

Sometimes you will find that even if you use mb_strlen , the result is still wrong. There are several possible reasons:

• The 'UTF-8' encoding is not specified explicitly, resulting in an error in the automatic judgment of the function;
• The string contains hidden characters (such as spaces, line breaks, emoji);
• The data source is not standardized, such as the data transmitted from the front end does not have a unified encoding format;
• When emoji emojis are included, some systems use them as two characters by default, and then use additional libraries or regular processing.

For example, suppose you take out a piece of content input from the database that is mixed with some invisible symbols. At this time, using mb_strlen directly may calculate less or more characters. It is recommended to clean up useless characters first and then calculate the length.

Ending

In general, in most practical development scenarios, mb_strlen() is preferred and the habit of specifying coding is developed. Unless you are very sure to only deal with ASCII characters, don't be lazy, otherwise it will be quite troublesome to troubleshoot.

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