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password_hash
Creates a password hash
Description
string password_hash(#[\SensitiveParameter]string $password, stringintnull $algo, array $options = [])
The following algorithms are currently supported:
-
PASSWORD_DEFAULT - Use the bcrypt algorithm (default as of PHP 5.5.0).
Note that this constant is designed to change over time as new and stronger algorithms are added
to PHP. For that reason, the length of the result from using this identifier can change over
time. Therefore, it is recommended to store the result in a database column that can expand
beyond 60 bytes (255 bytes would be a good choice).
-
PASSWORD_BCRYPT - Use the bcrypt algorithm to
create the hash. This will produce a standard crypt compatible hash using
the $2y$ identifier.
-
PASSWORD_ARGON2I - Use the Argon2i hashing algorithm to create the hash.
This algorithm is only available if PHP has been compiled with Argon2 support.
-
PASSWORD_ARGON2ID - Use the Argon2id hashing algorithm to create the hash.
This algorithm is only available if PHP has been compiled with Argon2 support.
Supported options for PASSWORD_BCRYPT:
-
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.
Warning
The salt option is deprecated. It is now
preferred to simply use the salt that is generated by default.
As of PHP 8.0.0, an explicitly given salt is ignored.
-
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 12 will be used. This is a good
baseline cost, but it should be adjusted depending on hardware used.
Supported options for PASSWORD_ARGON2I
and PASSWORD_ARGON2ID:
-
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.
Warning
Only available when PHP uses libargon2, not with libsodium implementation.
Parameters
-
password
-
The user's password.
Caution
Using the PASSWORD_BCRYPT as the
algorithm, will result
in the password parameter being truncated to a
maximum length of 72 bytes.
-
algo
-
A password algorithm constant denoting the algorithm to use when hashing the password.
-
options
-
An associative array containing options. See the password algorithm constants for documentation on the supported options for each algorithm.
Return Values
Returns the hashed password.
The used algorithm, cost and salt are returned as part of the hash. Therefore,
all information that's needed to verify the hash is included in it. This allows
the password_verify function to verify the hash without
needing separate storage for the salt or algorithm information.
Examples
Example #1 password_hash example
<?php
echo password_hash("rasmuslerdorf", PASSWORD_DEFAULT);
?>
The above example will output
something similar to:
$2y$12$4Umg0rCJwMswRw/l.SwHvuQV01coP0eWmGzd61QH2RvAOMANUBGC.
Example #2 password_hash example setting cost manually
<?php
$options = [
// Increase the bcrypt cost from 12 to 13.
'cost' => 13,
];
echo password_hash("rasmuslerdorf", PASSWORD_BCRYPT, $options);
?>
The above example will output
something similar to:
$2y$13$xeDfQumlmdm0Sco.4qmH1OGfUUmOcuRmfae0dPJhjX1Bq0yYhqbNi
Example #3 password_hash example finding a good cost
This code will benchmark the machine to determine how high of a cost can be used
without deteriorating user experience. It is recommended to set the highest cost
that does not slow down other operations the machine needs to perform. 11 is a
good baseline, and more is better if the machine is fast enough. The code below
aims for ≤ 350 milliseconds stretching time, which is an appropriate delay for
systems handling interactive logins.
<?php
$timeTarget = 0.350; // 350 milliseconds
$cost = 11;
do {
$cost++;
$start = microtime(true);
password_hash("test", PASSWORD_BCRYPT, ["cost" => $cost]);
$end = microtime(true);
} while (($end - $start) < $timeTarget);
echo "Appropriate Cost Found: " . $cost - 1;
?>
The above example will output
something similar to:
Appropriate Cost Found: 13
Example #4 password_hash example using Argon2i
<?php
echo 'Argon2i hash: ' . password_hash('rasmuslerdorf', PASSWORD_ARGON2I);
?>
The above example will output
something similar to:
Argon2i hash: $argon2i$v=19$m=1024,t=2,p=2$YzJBSzV4TUhkMzc3d3laeg$zqU/1IN0/AogfP4cmSJI1vc8lpXRW9/S0sYY2i2jHT0
Notes
Caution
It is strongly recommended not to provide an explicit salt for this function.
A secure salt will automatically be created if no salt is specified.
As noted above, providing the salt option in PHP 7.0.0
will generate a deprecation warning. Support for providing a salt explicitly
has been removed in PHP 8.0.0.
Note:
It is recommended to test this function on the machine used, adjusting the cost parameter(s)
so that execution of the function takes less than 350 milliseconds for interactive logins.
The script in the above example will help choosing an appropriate bcrypt cost for the given
machine.
Note:
Updates to supported algorithms by this function (or changes to the default one) must follow
the following rules:
-
Any new algorithm must be in core for at least 1 full release of PHP
prior to becoming default. So if, for example, a new algorithm is added
in 7.5.5, it would not be eligible for default until 7.7 (since 7.6
would be the first full release). But if a different algorithm was added
in 7.6.0, it would also be eligible for default at 7.7.0.
-
The default should only change in a full release (7.3.0, 8.0.0, etc)
and not in a revision release. The only exception to this is in an
emergency when a critical security flaw is found in the current
default.
See Also
- password_verify
- password_needs_rehash
- crypt
- sodium_crypto_pwhash_str
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