# grapheme_extract

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

grapheme_extract — Function to extract a sequence of default grapheme clusters from a text buffer, which must be encoded in UTF-8

### 说明

过程化风格

grapheme_extract ( string `$haystack` , int `$size` [, int `$extract_type` [, int `$start` = 0 [, int `&$next` ]]] ) : string

Function to extract a sequence of default grapheme clusters from a text buffer, which must be encoded in UTF-8.

### 参数

`haystack`

  String to search.

`size`

  Maximum number items - based on the $extract_type - to return.

`extract_type`

  Defines the type of units referred to by the $size parameter:

  - GRAPHEME_EXTR_COUNT (default) - $size is the number of default grapheme clusters to extract.
  - GRAPHEME_EXTR_MAXBYTES - $size is the maximum number of bytes returned.
  - GRAPHEME_EXTR_MAXCHARS - $size is the maximum number of UTF-8 characters returned.
`start`

  Starting position in $haystack in bytes - if given, it must be zero or a positive value that is less than or equal to the length of $haystack in bytes, or a negative value that counts from the end of $haystack. If $start does not point to the first byte of a UTF-8 character, the start position is moved to the next character boundary.

`next`

  Reference to a value that will be set to the next starting position. When the call returns, this may point to the first byte position past the end of the string.

### 返回值

A string starting at offset $start and ending on a default grapheme cluster boundary that conforms to the $size and $extract_type specified.

### 更新日志

版本 | 说明
--- | ---
7.1.0 | Support for negative `start`s has been added.

### 范例

Example #1 grapheme_extract() 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_extract( $char_a_ring_nfd . $char_o_diaeresis_nfd, 1, GRAPHEME_EXTR_COUNT, 2));

    ?>

以上例程会输出：

    o%CC%88

### 参见

- grapheme_substr() - Return part of a string
- » Unicode Text Segmentation: Grapheme Cluster Boundaries