PASSWORD_HASH(3) 1 PASSWORD_HASH(3)
password_hash - Creates a password hash
SYNOPSIS
string password_hash (string $password, integer $algo, [array $options])
DESCRIPTION
password_hash(3) creates a new password hash using a strong one-way hashing algorithm. password_hash(3) is compatible with crypt(3). There-
fore, password hashes created by crypt(3) can be used with password_hash(3).
The following algorithms are currently supported:
o 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 characters (255 characters
would be a good choice).
o PASSWORD_BCRYPT - Use the CRYPT_BLOWFISH algorithm to create the hash. This will produce a standard crypt(3) compatible hash using
the "$2y$" identifier. The result will always be a 60 character string, or FALSE on failure. Supported Options:
o salt - 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(3) for each password hashed.
This is the intended mode of operation.
o cost - which denotes the algorithmic cost that should be used. Examples of these values can be found on the crypt(3) 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.
PARAMETERS
o $password
- The user's password.
Caution
Using the PASSWORD_BCRYPT for the $algo parameter, will result in the $password parameter being truncated to a maximum
length of 72 characters.
o $algo
- A password algorithm constant denoting the algorithm to use when hashing the password.
o $options
- An associative array containing options. See the password algorithm constants for documentation on the supported options for
each algorithm. If omitted, a random salt will be created and the default cost will be used.
RETURN VALUES
Returns the hashed password, or FALSE on failure.
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(3) function to verify the hash without needing separate storage for the salt or algorithm
information.
EXAMPLES
Example #1
password_hash(3) example
<?php
/**
* We just want to hash our password using the current DEFAULT algorithm.
* This is presently BCRYPT, and will produce a 60 character result.
*
* Beware that DEFAULT may change over time, so you would want to prepare
* By allowing your storage to expand past 60 characters (255 would be good)
*/
echo password_hash("rasmuslerdorf", PASSWORD_DEFAULT)."
";
?>
The above example will output something similar to:
$2y$10$.vGA1O9wmRjrwAVXD98HNOgsNpDczlqm3Jq7KnEd1rVAGv3Fykk1a
Example #2
password_hash(3) example setting cost manually
<?php
/**
* In this case, we want to increase the default cost for BCRYPT to 12.
* Note that we also switched to BCRYPT, which will always be 60 characters.
*/
$options = [
'cost' => 12,
];
echo password_hash("rasmuslerdorf", PASSWORD_BCRYPT, $options)."
";
?>
The above example will output something similar to:
$2y$12$QjSH496pcT5CEbzjD/vtVeH03tfHKFy36d4J0Ltp3lRtee9HDxY3K
Example #3
password_hash(3) example setting salt manually
<?php
/**
* Note that the salt here is randomly generated.
* Never use a static salt or one that is not randomly generated.
*
* For the VAST majority of use-cases, let password_hash generate the salt randomly for you
*/
$options = [
'cost' => 11,
'salt' => mcrypt_create_iv(22, MCRYPT_DEV_URANDOM),
];
echo password_hash("rasmuslerdorf", PASSWORD_BCRYPT, $options)."
";
?>
The above example will output something similar to:
$2y$11$q5MkhSBtlsJcNEVsYh64a.aCluzHnGog7TQAKVmQwO9C8xb.t89F.
Example #4
password_hash(3) example finding a good cost
<?php
/**
* This code will benchmark your server to determine how high of a cost you can
* afford. You want to set the highest cost that you can without slowing down
* you server too much. 8-10 is a good baseline, and more is good if your servers
* are fast enough. The code below aims for <= 50 milliseconds stretching time,
* which is a good baseline for systems handling interactive logins.
*/
$timeTarget = 0.05; // 50 milliseconds
$cost = 8;
do {
$cost++;
$start = microtime(true);
password_hash("test", PASSWORD_BCRYPT, ["cost" => $cost]);
$end = microtime(true);
} while (($end - $start) < $timeTarget);
echo "Appropriate Cost Found: " . $cost . "
";
?>
The above example will output something similar to:
Appropriate Cost Found: 10
NOTES
Caution
It is strongly recommended that you do not generate your own salt for this function. It will create a secure salt automatically for
you if you do not specify one.
Note
It is recommended that you test this function on your servers, and adjust the cost parameter so that execution of the function
takes less than 100 milliseconds on interactive systems. The script in the above example will help you choose a good cost value for
your hardware.
Note
Updates to supported algorithms by this function (or changes to the default one) must follow the following rules:
oAny 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 5.5.5, it would not be eligible for default until 5.7 (since 5.6 would be the first full release). But
if a different algorithm was added in 5.6.0, it would also be eligible for default at 5.7.0.
o The default should only change on a full release (5.6.0, 6.0.0, etc) and not on 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(3), crypt(3), userland implementation.
PHP Documentation Group PASSWORD_HASH(3)