A brief analysis of how many bytes a character occupies in PHP

PHP is a widely used programming language and very popular. When writing PHP code, developers often need knowledge of how many bytes a PHP character occupies. This question sounds simple, but it actually involves many different aspects and situations.

PHP Character Encoding

Before answering this question, we need to understand PHP character encoding first. Character encoding is the process of converting characters into a computer-readable binary format. PHP supports multiple character encodings, including ASCII, UTF-8, ISO-8859, Windows 1252, etc.

ASCII encoding is the most basic character encoding. An ASCII character occupies one byte in memory, that is, 8 bits. It includes English letters, numbers, symbols and some control characters. In PHP, you can use the ord() function to obtain the ASCII code of an ASCII character.

UTF-8 encoding is a variable-length character encoding used to represent Unicode encoding. In UTF-8, a character can consist of one or more bytes. Normally, an English letter or number occupies one byte in UTF-8, while a Chinese character occupies three bytes in UTF-8.

ISO-8859 and Windows 1252 encoding is a single-byte character encoding used to represent characters in Western European languages. In these encodings, each character occupies one byte.

How many bytes does one character occupy in PHP?

Now back to the question itself: How many bytes does one character occupy in PHP? Since PHP supports multiple character encodings, the answer depends on the type of encoding used and the characters themselves. Below we discuss the number of bytes occupied by the next character in ASCII, UTF-8, ISO-8859 and Windows 1252 encoding respectively.

• ASCII encoding

In ASCII encoding, each character is represented by a byte, so one ASCII character occupies one byte. This is true whether it is English letters, numbers or symbols.

• UTF-8 encoding

In UTF-8 encoding, a character can be composed of one or more bytes. UTF-8 uses variable length encoding, using 1-4 bytes to represent a character depending on the character. Normally, an English letter or number occupies one byte in UTF-8, while a Chinese character occupies three bytes in UTF-8.

For example:

$str1 = 'hello'; $str2 = '你好'; echo strlen($str1); // 输出 5 echo strlen($str2); // 输出 6

In the above example, the string $str1 contains 5 characters, each character occupies one byte, so the length of the string is 5. The string $str2 contains 2 Chinese characters and one English character. Each Chinese character occupies 3 bytes and the English character occupies 1 byte, so the length of the string is 6.

• ISO-8859 and Windows 1252 encoding

In ISO-8859 and Windows 1252 encoding, each character occupies one byte. So whether it's English letters, numbers, symbols or special characters in Western European languages.

Conclusion

In general, the number of bytes occupied by a character in PHP depends on the character encoding used and the character itself. In ASCII encoding, each character occupies one byte; in UTF-8 encoding, one English letter or number occupies one byte, and one Chinese character generally occupies three bytes; in ISO-8859 and Windows 1252 encoding , each character occupies one byte.

Therefore, when writing PHP code, you need to pay attention to character encoding and character length issues, especially when dealing with multi-language character sets.

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