strnatcmp

(PHP 4, PHP 5, PHP 7, PHP 8)

strnatcmp使用自然排序算法比较字符串

说明

strnatcmp(string $string1, string $string2): int

该函数实现了以人类习惯对数字型字符串进行排序的比较算法,这就是“自然顺序”。注意该比较区分大小写。

参数

string1

第一个字符串。

string2

第二个字符串。

返回值

如果 string1 小于 string2,则返回小于 0 的值; 如果 string1 大于 string2,则返回大于 0 的值; 如果它们相等,则返回 0。 除了它的符号外,不能从返回值中可靠推断出任何特定的含义。

更新日志

版本 说明
8.2.0 当字符串长度不相等时,此函数不再保证返回 strlen($string1) - strlen($string2), 而可能返回 -11

示例

下面的例子展示了该算法与计算机常规字符串比较算法(strcmp() 所使用的)的区别:

<?php
$arr1
= $arr2 = array("img12.png", "img10.png", "img2.png", "img1.png");
echo
"Standard string comparison\n";
usort($arr1, "strcmp");
print_r($arr1);
echo
"\nNatural order string comparison\n";
usort($arr2, "strnatcmp");
print_r($arr2);
?>

以上示例会输出:

Standard string comparison
Array
(
    [0] => img1.png
    [1] => img10.png
    [2] => img12.png
    [3] => img2.png
)

Natural order string comparison
Array
(
    [0] => img1.png
    [1] => img2.png
    [2] => img10.png
    [3] => img12.png
)
更多信息,参见:Martin Pool 的» 自然顺序的字符串比较 page.

参见

  • preg_match() - 执行匹配正则表达式
  • strcasecmp() - 二进制安全比较字符串(不区分大小写)
  • substr() - 返回字符串的子串
  • stristr() - strstr 函数的忽略大小写版本
  • strcmp() - 二进制安全字符串比较
  • strncmp() - 二进制安全比较字符串开头的若干个字符
  • strncasecmp() - 二进制安全比较字符串开头的若干个字符(不区分大小写)
  • strnatcasecmp() - 使用“自然顺序”算法比较字符串(不区分大小写)
  • strstr() - 查找字符串的首次出现
  • natsort() - 用“自然排序”算法对数组排序
  • natcasesort() - 用“自然排序”算法对数组进行不区分大小写字母的排序

添加备注

用户贡献的备注 4 notes

up
7
in dot games dot mq at gmail dot com
8 years ago
Can also be used with combination of a compare for an array nested value, like<?php$array = array(    "city" => "xyz",    "names" => array(        array(            "name" => "Ana2",            "id" => 1        ) ,        array(            "name" => "Ana1",            "id" => 2        )    ));usort($array["names"], function ($a, $b)    {    return strnatcmp($a['name'], $b['name']);} );
up
2
thomas at uninet dot se
19 years ago
There seems to be a bug in the localization for strnatcmp and strnatcasecmp. I searched the reported bugs and found a few entries which were up to four years old (but the problem still exists when using swedish characters).These functions might work instead.<?phpfunction _strnatcasecmp($left, $right) {  return _strnatcmp(strtolower($left), strtolower($right));}function _strnatcmp($left, $right) {  while((strlen($left) > 0) && (strlen($right) > 0)) {    if(preg_match('/^([^0-9]*)([0-9].*)$/Us', $left, $lMatch)) {      $lTest = $lMatch[1];      $left = $lMatch[2];    } else {      $lTest = $left;      $left = '';    }    if(preg_match('/^([^0-9]*)([0-9].*)$/Us', $right, $rMatch)) {      $rTest = $rMatch[1];      $right = $rMatch[2];    } else {      $rTest = $right;      $right = '';    }    $test = strcmp($lTest, $rTest);    if($test != 0) {      return $test;    }    if(preg_match('/^([0-9]+)([^0-9].*)?$/Us', $left, $lMatch)) {      $lTest = intval($lMatch[1]);      $left = $lMatch[2];    } else {      $lTest = 0;    }    if(preg_match('/^([0-9]+)([^0-9].*)?$/Us', $right, $rMatch)) {      $rTest = intval($rMatch[1]);      $right = $rMatch[2];    } else {      $rTest = 0;    }    $test = $lTest - $rTest;    if($test != 0) {      return $test;    }  }  return strcmp($left, $right);}?>The code is not optimized. It was just made to solve my problem.
up
-1
chris at ocproducts dot com
8 years ago
This function has some interesting behaviour on strings consisting of mixed numbers and letters.One may expect that such a mixed string would be treated as alpha-numeric, but that is not true.var_dump(strnatcmp('23','123')); →int(-1)As expected, 23<123   (even though first digit is higher, overall number is smaller)var_dump(strnatcmp('yz','xyz')); →int(1)As expected, yz>xyz   (string comparison, irregardless of string length)var_dump(strnatcmp('2x','12y')); →int(-1)Remarkable, 2x<12y    (does a numeric comparison)var_dump(strnatcmp('20x','12y'));int(1)Remarkable, 20x>12y    (does a numeric comparison)It seems to be splitting what is being compared into runs of numbers and letters, and then comparing each run in isolation, until it has an ordering difference.
up
-4
spamspamspam at gmx dot com
6 years ago
Some more remarkable outcomes:var_dump(strnatcmp("0.15m", "0.2m"));int(1)var_dump(strnatcmp("0.15m", "0.20m"));int(-1)It's not about localisation:var_dump(strnatcmp("0,15m", "0,2m"));int(1)var_dump(strnatcmp("0,15m", "0,20m"));int(-1)
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