crc32()

(PHP 4 >= 4.0.1, PHP 5, PHP 7)

计算一个字符串的 crc32 多项式

说明

生成$str的 32 位循环冗余校验码多项式。这通常用于检查传输的数据是否完整。

由于 PHP 的整数是带符号的，所以在 32 位系统上许多 crc32 校验码将返回负整数。尽管在 64 位上所有crc32()的结果将都是正整数。

因此你需要使用sprintf()或printf()的“%u”格式符来获取表示无符号 crc32 校验码的字符串。

For a hexadecimal representation of the checksum you can either use the "%x" formatter ofsprintf()orprintf()or thedechex()conversion functions, both of these also take care of converting thecrc32()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 generichash().hash("crc32b",$str)will return the same string asdechex(crc32($str)).

参数

要校验的数据。

返回值

返回$strcrc32 校验的整数。

范例

显示一个 crc32 校验码

示例中的第二行演示了如何使用printf()函数转换校验码：

参见

• hash()生成哈希值（消息摘要）
• md5()计算字符串的 MD5 散列值
• sha1()计算字符串的 sha1 散列值

This function returns an unsigned integer from a 64-bit Linux platform. It does return the signed integer from other 32-bit platforms even a 64-bit Windows one.
The reason is because the two constants PHP_INT_SIZE and PHP_INT_MAX have different values on the 64-bit Linux platform.
I've created a work-around function to handle this situation.

Hope this helps.

The khash() function by sukitsupaluk has two problems, it does not use all 62 characters from the $map set and when corrected it then produces different results on 64-bit compared to 32-bit PHP systems.
Here is my modified version :

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