Using mb_substr() for Multibyte-Safe Substring Extraction in PHP

The mb_substr() function in PHP performs a multibyte‑safe substring operation, allowing you to extract a portion of a string based on character count rather than byte count.

Signature: string mb_substr(string $str, int $start, int $length = NULL, string $encoding = mb_internal_encoding()) .

Parameters:

str : the input string.

start : the zero‑based position of the first character to include.

length : the maximum number of characters to extract; if omitted or NULL, extracts to the end of the string.

encoding : the character encoding to use; defaults to the internal encoding.

Return value: the extracted substring according to the specified start, length, and encoding.

Example 1 – extracting the first two characters of a Chinese string:

<?php
echo mb_substr("我是菜鸟", 0, 2);
// Output: 我是
?>

Example 2 – specifying UTF‑8 encoding and extracting four characters:

<?php
header("content-type:text/html; charset=utf-8");
$string = "你好我好大家好";
echo mb_substr($string, 0, 4, 'utf-8');
// Output: 你好我好
?>