mbstring

mbstring is a PHP extension that provides multibyte string handling to support encodings such as UTF-8 and other non‑single-byte character sets. It enables encoding-aware operations on strings, ensuring that characters are not inadvertently split or corrupted during processing.

The extension offers a broad set of functions prefixed with mb_ for common string tasks. Examples include mb_strlen and mb_substr for length and substring operations, mb_strpos and mb_strrpos for searching within multibyte strings, and mb_strtolower and mb_strtoupper for case conversion. Additional utilities cover string trimming, trimming by width, width calculation, and safe conversion between encodings via mb_convert_encoding. It also provides multibyte regular expression support through related functions, and facilities for detecting and configuring encodings, such as mb_detect_encoding and mb_internal_encoding.

mbstring relies on a configured internal encoding and can handle a variety of character sets beyond UTF-8. Applications should explicitly set the internal encoding with mb_internal_encoding and, where necessary, specify the encoding in function calls to avoid ambiguity. The extension often collaborates with other PHP encoding tools, such as iconv, and can be used in conjunction with multibyte-aware regular expressions.

Installation and configuration vary by platform. mbstring is commonly bundled with PHP and enabled in php.ini (for example, extension=mbstring.so on Unix-like systems or enabling the PHP_MBSTRING module on Windows). On many distributions, it is available as a separate package (for instance, php-mbstring). Proper enabling and encoding configuration are important for correct operation across multilingual input and output.

Related topics include Unicode, UTF-8, and multibyte character sets.