crc32
(PHP 4 >= 4.0.1, PHP 5, PHP 7, PHP 8)
crc32 — 計算一個字串的 crc32 多項式
說明
$str): int
產生 str
的 32 位循環冗餘校驗碼多項式。這通常用於檢查傳輸的數據是否完整。
由於 PHP 的整數是帶符號的，所以在 32 位系統上許多 crc32 校驗碼將返回負整數。 儘管在 64 位上所有 crc32() 的結果將都是正整數。
因此你需要使用 sprintf() 或 printf() 的「%u」格式符來獲取表示無符號 crc32 校驗碼的字串。
For a hexadecimal representation of the checksum you can either use the "%x" formatter of sprintf() or printf() or the dechex() conversion functions, both of these also take care of converting the crc32() result to an unsigned integer.
Having 64bit installations also return negative integers for higher result values was considered but would break the hexadecimal conversion as negatives would get an extra 0xFFFFFFFF######## offset then. As hexadecimal representation seems to be the most common use case we decided to not break this even if it breaks direct decimal comparisons in about 50% of the cases when moving from 32 to 64bits.
In retrospect having the function return an integer maybe wasn't the best idea and returning a hex string representation right away (as e.g. md5() does) might have been a better plan to begin with.
For a more portable solution you may also consider the generic
hash(). hash("crc32b", $str) will
return the same string as dechex(crc32($str)).
參數
-
str -
要校驗的數據。
返回值
返回 str crc32 校驗的整數。
範例
示例 #1 顯示一個 crc32 校驗碼
示例中的第二行演示瞭如何使用 printf() 函式轉換校驗碼：
<?php
$checksum = crc32("The quick brown fox jumped over the lazy dog.");
printf("%u\n", $checksum);
?>