(PHP 4, PHP 5, PHP 7, PHP 8)
strnatcmp — "自然順"アルゴリズムにより文字列比較を行う
この関数は、人間が行うような手法でアルファベットまたは数字の 文字列の順序を比較するアルゴリズムを実装します。この手法は、"自然順" と言われます。 この比較は、大文字小文字を区別することに注意してください。
string1最初の文字列。
string2次の文字列。
他の文字列比較関数と同様に、この関数は、
string1 が string2
より小さいに場合に -1、string1 が
string2 より大きい場合に 1、等しい場合に
0 を返します。
| バージョン | 説明 |
|---|---|
| 8.2.0 |
これより前のバージョンで負の数と正の数を返していた場合に、
この関数は -1 と 1 を返すようになりました。
|
このアルゴリズムと (strcmp() を使用した) 通常のコンピュータ文字列ソートの間の違いの例を次に示します。
<?php
$arr1 = $arr2 = array("img12.png", "img10.png", "img2.png", "img1.png");
echo "標準の文字列比較\n";
usort($arr1, "strcmp");
print_r($arr1);
echo "\n自然順での文字列比較\n";
usort($arr2, "strnatcmp");
print_r($arr2);
?>上の例の出力は以下となります。
標準の文字列比較
Array
(
[0] => img1.png
[1] => img10.png
[2] => img12.png
[3] => img2.png
)
自然順での文字列比較
Array
(
[0] => img1.png
[1] => img2.png
[2] => img10.png
[3] => img12.png
)
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'], $b['name']);} );There seems to be a bug in the localization for strnatcmp and strnatcasecmp. I searched the reported bugs and found a few entries which were up to four years old (but the problem still exists when using swedish characters).
These functions might work instead.
<?php
function _strnatcasecmp($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.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.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)