密码散列算法

## 简介
密码散列算法 API 提供了 crypt() 等密码算法的简单易用包装， 以一种简洁易用安全的方式创建和管理密码。

## 安装/配置

### 需求
构建此扩展不需要其他扩展。

为了支持 Argon2 密码散列，需要 [» libargon2](https://github.com/P-H-C/phc-winner-argon2 "» libargon2")。 PHP 7.3.0 起，需要 libargon2 为 20161029 或更高的版本。

### 安装
使用这些函数不需要安装，它们是 PHP 核心的一部分。

为了使用 Argon2 密码散列，PHP 必须用 --with-password-argon2 配置选项和 libargon2 构建。

在 PHP 8.1.0 之前，可以使用 --with-password-argon2[=DIR] 指定 argon2 目录。

### 运行时配置
此扩展没有在 `php.ini` 中定义配置指令。

### 资源类型
此扩展没有定义资源类型。

## 预定义常量
下列常量作为 PHP 核心的一部分总是可用的。

PASSWORD_BCRYPT (string)
PASSWORD_BCRYPT is used to create new password hashes using the CRYPT_BLOWFISH algorithm.

This will always result in a hash using the "$2y$" crypt format, which is always 60 characters wide.

Supported Options:

- salt (string) - to manually provide a salt to use when hashing the password. Note that this will override and prevent a salt from being automatically generated.

If omitted, a random salt will be generated by password_hash() for each password hashed. This is the intended mode of operation and as of PHP 7.0.0 the salt option has been deprecated.

- cost (int) - which denotes the algorithmic cost that should be used. Examples of these values can be found on the crypt() page.

If omitted, a default value of 10 will be used. This is a good baseline cost, but you may want to consider increasing it depending on your hardware.

`PASSWORD_BCRYPT_DEFAULT_COST` (`int`)

`PASSWORD_ARGON2I` (`string`)
PASSWORD_ARGON2I is used to create new password hashes using the Argon2i algorithm.

Supported Options:

- memory_cost (int) - Maximum memory (in kibibytes) that may be used to compute the Argon2 hash. Defaults to `PASSWORD_ARGON2_DEFAULT_MEMORY_COST`.

- time_cost (int) - Maximum amount of time it may take to compute the Argon2 hash. Defaults to `PASSWORD_ARGON2_DEFAULT_TIME_COST`.

- threads (int) - Number of threads to use for computing the Argon2 hash. Defaults to `PASSWORD_ARGON2_DEFAULT_THREADS`. Only available with libargon2, not with libsodium implementation.

Available as of PHP 7.2.0.
`
`PASSWORD_ARGON2ID` (string`)
`PASSWORD_ARGON2ID` is used to create new password hashes using the Argon2id algorithm. It supports the same options as `PASSWORD_ARGON2I`.

Available as of PHP 7.3.0.

`PASSWORD_ARGON2_DEFAULT_MEMORY_COST` (`int`)
Default amount of memory in bytes that will be used while trying to compute a hash.

Available as of PHP 7.2.0.

`PASSWORD_ARGON2_DEFAULT_TIME_COST` (`int`)
Default amount of time that will be spent trying to compute a hash.

Available as of PHP 7.2.0.

`PASSWORD_ARGON2_DEFAULT_THREADS` (`int`)
Default number of threads that Argon2lib will use. Not available with libsodium implementation.

Available as of PHP 7.2.0.

`PASSWORD_ARGON2_PROVIDER` (`string`)
Available as of PHP 7.4.0.

`PASSWORD_DEFAULT` (`mixed`)
The default algorithm to use for hashing if no algorithm is provided. This may change in newer PHP releases when newer, stronger hashing algorithms are supported.

It is worth noting that over time this constant can (and likely will) change. Therefore you should be aware that the length of the resulting hash can change. Therefore, if you use PASSWORD_DEFAULT you should store the resulting hash in a way that can store more than 60 characters (255 is the recommended width).

Values for this constant:

- PHP 5.5.0 - `PASSWORD_BCRYPT`

**更新日志**

| 版本    | 说明       |
|-------|---------------|
| 7.4.0 | The values of the password algo IDs (PASSWORD_BCRYPT, PASSWORD_ARGON2I, PASSWORD_ARGON2ID and PASSWORD_DEFAULT) are now strings. Previously, they have been ints. |