mbstrlen

mbstrlen is commonly used to refer to the multibyte string length function mb_strlen, which is provided by the mbstring extension in PHP. It counts the number of characters in a string rather than the number of bytes by interpreting the string according to a specified character encoding.

The function counts characters according to the given encoding. If no encoding is supplied, mb_strlen uses the internal encoding configured for mbstring. This makes it suitable for strings containing multibyte characters such as UTF-8, where a single character may occupy multiple bytes.

Syntax: mb_strlen(string $string, string|null $encoding = null)

Parameters: $string is the input string. $encoding is an optional encoding name, such as 'UTF-8', 'ISO-8859-1', or others supported by mbstring. If encoding is omitted, the internal mbstring encoding is used.

Return value: The function returns an integer representing the number of characters in the string for the specified encoding. If the string contains invalid byte sequences for the given encoding or another error occurs, the function may return false or emit a warning depending on the runtime configuration.

Examples: mb_strlen('hello', 'UTF-8') returns 5. mb_strlen('こんにちは', 'UTF-8') returns 5, illustrating its multibyte awareness.

Notes: mb_strlen counts code points (characters) for the specified encoding, not grapheme clusters. For grapheme-aware length, additional libraries or techniques may be required. mb_strlen is part of the mbstring extension and requires it to be enabled in the PHP installation.

See also: strlen, mb_strpos, mb_substr, mb_strwidth, mb_detect_encoding.