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password_hash
Creates a password hash
Description
string password_hash
( string $password
, integer $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 characters (255 characters would be a good choice).
-
PASSWORD_BCRYPT - Use the CRYPT_BLOWFISH algorithm to
create the hash. This will produce a standard crypt compatible hash using
the "$2y$" identifier. The result will always be a 60 character string, or FALSE on failure.
Supported Options:
-
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 for
each password hashed. This is the intended mode of operation.
-
cost - 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.
Parameters
-
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. This is only a concern if are using
the same salt to hash strings with this algorithm that are over 72
bytes in length, as this will result in those hashes being identical.
-
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.
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 function to verify the hash without
needing separate storage for the salt or algorithm information.
Examples
Example #1 password_hash 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)."\n";
?>
The above example will output
something similar to:
$2y$10$.vGA1O9wmRjrwAVXD98HNOgsNpDczlqm3Jq7KnEd1rVAGv3Fykk1a
Example #2 password_hash 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)."\n";
?>
The above example will output
something similar to:
$2y$12$QjSH496pcT5CEbzjD/vtVeH03tfHKFy36d4J0Ltp3lRtee9HDxY3K
Example #3 password_hash 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)."\n";
?>
The above example will output
something similar to:
$2y$11$q5MkhSBtlsJcNEVsYh64a.aCluzHnGog7TQAKVmQwO9C8xb.t89F.
Example #4 password_hash 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. 10 is a good baseline, and more is good if your servers
* are fast enough.
*/
$timeTarget = 0.2;
$cost = 9;
do {
$cost++;
$start = microtime(true);
password_hash("test", PASSWORD_BCRYPT, ["cost" => $cost]);
$end = microtime(true);
} while (($end - $start) < $timeTarget);
echo "Appropriate Cost Found: " . $cost . "\n";
?>
The above example will output
something similar to:
Appropriate Cost Found: 11
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 should test this function on your servers, and adjust the cost
parameter so that execution of the function takes approximately 0.1 to 0.5 seconds. 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 follwoing 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 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.
-
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.
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