Return part of a string

# grapheme_substr

(PHP 5 >= 5.3.0, PHP 7, PHP 8, PECL intl >= 1.0.0)

grapheme_substr — Return part of a string

### 说明

过程化风格

function grapheme_substr(
string `$string`,
int `$offset`,
?int `$length` = `null`,
string `$locale` = ""
): string|false

Return part of a string

### 参数

`string`

  The input string. Must be valid UTF-8.

`offset`

  Start position in default grapheme units. If `offset` is non-negative, the returned string will start at the `offset`'th position in `string`, counting from zero. If `offset` is negative, the returned string will start at the `offset`'th grapheme unit from the end of string.

`length`

  Length in grapheme units. If `length` is given and is positive, the string returned will contain at most `length` grapheme units beginning from `offset` (depending on the length of string). If `length` is given and is negative, then that many grapheme units will be omitted from the end of string (after the start position has been calculated when `offset` is negative). If `offset` denotes a position beyond this truncation, an empty string will be returned.

`locale`
  要使用的区域设置。

### 返回值

Returns the extracted part of `string`, 或者在失败时返回 `false`.

### 更新日志

版本 | 说明
--- | ---
8.5.0 | 已新增可选参数 `locale`。
8.0.0 | The function now consistently clamps out-of-bounds offsets to the string boundary. Previously, `false` was returned instead of the empty string in some cases.

### 示例

示例 #1 grapheme_substr() example

    <?php

    $char_a_ring_nfd = "a\xCC\x8A";  // 'LATIN SMALL LETTER A WITH RING ABOVE' (U+00E5) normalization form "D"
    $char_o_diaeresis_nfd = "o\xCC\x88"; // 'LATIN SMALL LETTER O WITH DIAERESIS' (U+00F6) normalization form "D"

    print urlencode(grapheme_substr( "ao" . $char_a_ring_nfd . "bc" . $char_o_diaeresis_nfd . "O", 2, -1 ));
    ?>

以上示例会输出：

    a%CC%8Abco%CC%88

### 参见

- grapheme_extract() - Function to extract a sequence of default grapheme clusters from a text buffer, which must be encoded in UTF-8
- » Unicode Text Segmentation: Grapheme Cluster Boundaries

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