mbstrpos

mbstrpos is commonly understood as the multibyte string search function used to locate the position of the first occurrence of a substring within a multibyte string. In standard PHP, the canonical function is mb_strpos, which is part of the mbstring extension. If you encounter a function named mbstrpos in code, it is usually a misnomer or a user-defined wrapper around mb_strpos rather than a separate, built-in PHP function.

The mb_strpos function searches for the first occurrence of a needle in a haystack while correctly handling multibyte encodings. Its typical signature is mb_strpos(string $haystack, string $needle, int $offset = 0, string $encoding = null). It returns the position as an integer counting from zero, or false if the needle is not found. The offset parameter specifies where to start the search, using character positions when multibyte characters are involved. The encoding parameter allows you to specify the character encoding; if it is null, the internal encoding is used.

If the needle is an empty string, PHP's behavior is to return 0, indicating that an empty string is found at the beginning. The mb_strpos function requires the mbstring extension to be enabled; without it, the multibyte-aware functionality will not be available. Related functions include mb_stripos (case-insensitive search) and mb_strrpos (searches from the end). Overall, mb_strpos enables reliable substring searches in Unicode and other multibyte-encoded texts, unlike the non-multibyte strpos.