grapheme_extract

(PHP 5 >= 5.3.0, PHP 7, PHP 8, 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 $type = GRAPHEME_EXTR_COUNT , int $offset = 0 , int &$next = null ) : string|false

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.

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.

offset

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, 或者在失败时返回 false.

更新日志

版本 说明
7.1.0 Support for negative offsets 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

User Contributed Notes

yevgen dot grytsay at gmail dot com 19-Oct-2020 01:35
Looping through grapheme clusters:

<?php

// Example taken from Rust documentation: https://doc.rust-lang.org/book/ch08-02-strings.html#bytes-and-scalar-values-and-grapheme-clusters-oh-my
$str = "??????";
// Alternatively:
//$str = pack('C*', ...[224, 164, 168, 224, 164, 174, 224, 164, 184, 224, 165, 141, 224, 164, 164, 224, 165, 135]);
$next = 0;
$maxbytes = strlen($str);

var_dump($str);

while ($next < $maxbytes) {
    $char = grapheme_extract($str, 1, GRAPHEME_EXTR_COUNT, $next, $next);
    if (empty($char)) {
        continue;
    }
    echo "{$char} - This utf8 character is " . strlen($char) . ' bytes long', PHP_EOL;
}

//string(18) "??????"
//? - This utf8 character is 3 bytes long
//? - This utf8 character is 3 bytes long
//?? - This utf8 character is 6 bytes long
//?? - This utf8 character is 6 bytes long
?>
AJH 12-Jul-2011 04:37
Here's how to use grapheme_extract() to loop across a UTF-8 string character by character.

<?php

$str = "?abc?'...";
// if the previous line didn't come through, the string contained:
//U+0633,U+0061,U+0062,U+0063,U+0915,U+2019,U+2026

$n = 0;

for (    $start = 0, $next = 0, $maxbytes = strlen($str), $c = '';
        $start < $maxbytes;
        $c = grapheme_extract($str, 1, GRAPHEME_EXTR_MAXCHARS , ($start = $next), $next)
    )
{
    if (empty($c))
        continue;
    echo "This utf8 character is " . strlen($c) . " bytes long and its first byte is " . ord($c[0]) . "\n";
    $n++;
}
echo "$n UTF-8 characters in a string of $maxbytes bytes!\n";
// Should print: 7 UTF8 characters in a string of 14 bytes!
?>