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<refentry xml:id="function.password-hash" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink">

<refnamediv>

<refname>password_hash</refname>

<refpurpose>Creates a password hash</refpurpose>

</refnamediv>

<refsect1 role="description">

&reftitle.description;

<methodsynopsis>

<type>string</type><methodname>password_hash</methodname>

<methodparam><modifier role="attribute">#[\SensitiveParameter]</modifier><type>string</type><parameter>password</parameter></methodparam>

<methodparam><type class="union"><type>string</type><type>int</type><type>null</type></type><parameter>algo</parameter></methodparam>

<methodparam choice="opt"><type>array</type><parameter>options</parameter><initializer>[]</initializer></methodparam>

</methodsynopsis>

<para>

<function>password_hash</function> creates a new password hash using a strong one-way hashing

algorithm.

</para>

<simpara>

The following algorithms are currently supported:

</simpara>

<para>

<itemizedlist>

<listitem>

<simpara>

<constant>PASSWORD_DEFAULT</constant> - 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).

</simpara>

</listitem>

<listitem>

<simpara>

<constant>PASSWORD_BCRYPT</constant> - Use the bcrypt algorithm to

create the hash. This will produce a standard <function>crypt</function> compatible hash using

the <literal>$2y$</literal> identifier. The result will always be a 60 character string, &return.falseforfailure;.

</simpara>

</listitem>

<listitem>

<simpara>

<constant>PASSWORD_ARGON2I</constant> - Use the Argon2i hashing algorithm to create the hash.

This algorithm is only available if PHP has been compiled with Argon2 support.

</simpara>

</listitem>

<listitem>

<simpara>

<constant>PASSWORD_ARGON2ID</constant> - Use the Argon2id hashing algorithm to create the hash.

This algorithm is only available if PHP has been compiled with Argon2 support.

</simpara>

</listitem>

</itemizedlist>

</para>

<simpara>

Supported options for <constant>PASSWORD_BCRYPT</constant>:

</simpara>

<para>

<itemizedlist>

<listitem>

<para>

<literal>salt</literal> (<type>string</type>) - to manually provide a salt to use when hashing the password.

Note that this will override and prevent a salt from being automatically generated.

</para>

<para>

If omitted, a random salt will be generated by <function>password_hash</function> for

each password hashed. This is the intended mode of operation.

</para>

<warning>

<para>

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.

</para>

</warning>

</listitem>

<listitem>

<para>

<literal>cost</literal> (<type>int</type>) - which denotes the algorithmic cost that should be used.

Examples of these values can be found on the <function>crypt</function> page.

</para>

<para>

If omitted, a default value of <literal>12</literal> will be used. This is a good

baseline cost, but you may want to consider adjusting it depending on your hardware.

</para>

</listitem>

</itemizedlist>

</para>

<simpara>

Supported options for <constant>PASSWORD_ARGON2I</constant>

and <constant>PASSWORD_ARGON2ID</constant>:

</simpara>

<para>

<itemizedlist>

<listitem>

<para>

<literal>memory_cost</literal> (<type>int</type>) - Maximum memory (in kibibytes) that may

be used to compute the Argon2 hash. Defaults to <constant>PASSWORD_ARGON2_DEFAULT_MEMORY_COST</constant>.

</para>

</listitem>

<listitem>

<para>

<literal>time_cost</literal> (<type>int</type>) - Maximum amount of time it may

take to compute the Argon2 hash. Defaults to <constant>PASSWORD_ARGON2_DEFAULT_TIME_COST</constant>.

</para>

</listitem>

<listitem>

<para>

<literal>threads</literal> (<type>int</type>) - Number of threads to use for computing

the Argon2 hash. Defaults to <constant>PASSWORD_ARGON2_DEFAULT_THREADS</constant>.

</para>

<warning>

<para>

Only available when PHP uses libargon2, not with libsodium implementation.

</para>

</warning>

</listitem>

</itemizedlist>

</para>

</refsect1>

<refsect1 role="parameters">

&reftitle.parameters;

<variablelist>

<varlistentry>

<term><parameter>password</parameter></term>

<listitem>

<para>

&password.parameter.password;

</para>

<caution>

<para>

Using the <constant>PASSWORD_BCRYPT</constant> as the

algorithm, will result

in the <parameter>password</parameter> parameter being truncated to a

maximum length of 72 bytes.

</para>

</caution>

</listitem>

</varlistentry>

<varlistentry>

<term><parameter>algo</parameter></term>

<listitem>

<para>

&password.parameter.algo;

</para>

</listitem>

</varlistentry>

<varlistentry>

<term><parameter>options</parameter></term>

<listitem>

<para>

&password.parameter.options;

</para>

</listitem>

</varlistentry>

</variablelist>

</refsect1>

<refsect1 role="returnvalues">

&reftitle.returnvalues;

<para>

Returns the hashed password.

</para>

<para>

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 <function>password_verify</function> function to verify the hash without

needing separate storage for the salt or algorithm information.

</para>

</refsect1>

<refsect1 role="changelog">

&reftitle.changelog;

<para>

<informaltable>

<tgroup cols="2">

<thead>

<row>

<entry>&Version;</entry>

<entry>&Description;</entry>

</row>

</thead>

<tbody>

<row>

<entry>8.4.0</entry>

<entry>

The default value of the <literal>cost</literal> option of the

<constant>PASSWORD_BCRYPT</constant> algorithm was increased from

<literal>10</literal> to <literal>12</literal>.

</entry>

</row>

<row>

<entry>8.3.0</entry>

<entry>

<function>password_hash</function> now sets the underlying

<exceptionname>Random\RandomException</exceptionname> as the

<property>Exception::$previous</property> exception when a

<exceptionname>ValueError</exceptionname> is thrown due to a failure

in the salt generation.

</entry>

</row>

<row>

<entry>8.0.0</entry>

<entry>

<function>password_hash</function> no longer returns &false; on failure, instead a

<classname>ValueError</classname> will be thrown if the password hashing algorithm

is not valid, or an <classname>Error</classname> if the password hashing failed

for an unknown error.

</entry>

</row>

<row>

<entry>8.0.0</entry>

<entry>

The <parameter>algo</parameter> parameter is nullable now.

</entry>

</row>

<row>

<entry>7.4.0</entry>

<entry>

The <parameter>algo</parameter> parameter expects a &string; now, but still accepts

&integer;s for backward compatibility.

</entry>

</row>

<row>

<entry>7.4.0</entry>

<entry>

The sodium extension provides an alternative implementation for Argon2 passwords.

</entry>

</row>

<row>

<entry>7.3.0</entry>

<entry>

Support for Argon2id passwords using <constant>PASSWORD_ARGON2ID</constant> was added.

</entry>

</row>

<row>

<entry>7.2.0</entry>

<entry>

Support for Argon2i passwords using <constant>PASSWORD_ARGON2I</constant> was added.

</entry>

</row>

</tbody>

</tgroup>

</informaltable>

</para>

</refsect1>

<refsect1 role="examples">

&reftitle.examples;

<para>

<example>

<title><function>password_hash</function> example</title>

<programlisting role="php">

<![CDATA[

<?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);

?>

]]>

</programlisting>

&example.outputs.similar;

<screen>

<![CDATA[

$2y$12$4Umg0rCJwMswRw/l.SwHvuQV01coP0eWmGzd61QH2RvAOMANUBGC.

]]>

</screen>

</example>

</para>

<para>

<example>

<title><function>password_hash</function> example setting cost manually</title>

<programlisting role="php">

<![CDATA[

<?php

/**

* In this case, we want to increase the cost for bcrypt to 13.

*/

$options = [

'cost' => 13,

];

echo password_hash("rasmuslerdorf", PASSWORD_BCRYPT, $options);

?>

]]>

</programlisting>

&example.outputs.similar;

<screen>

<![CDATA[

$2y$13$xeDfQumlmdm0Sco.4qmH1OGfUUmOcuRmfae0dPJhjX1Bq0yYhqbNi

]]>

</screen>

</example>

</para>

<para>

<example>

<title><function>password_hash</function> example finding a good cost</title>

<programlisting role="php">

<![CDATA[

<?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. 11 is a good baseline, and more is good if your servers

* are fast enough. The code below aims for ≤ 350 milliseconds stretching time,

* which is an appropriate delay for systems handling interactive logins.

*/

$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;

?>

]]>

</programlisting>

&example.outputs.similar;

<screen>

<![CDATA[

Appropriate Cost Found: 13

]]>

</screen>

</example>

</para>

<para>

<example>

<title><function>password_hash</function> example using Argon2i</title>

<programlisting role="php">

<![CDATA[

<?php

echo 'Argon2i hash: ' . password_hash('rasmuslerdorf', PASSWORD_ARGON2I);

?>

]]>

</programlisting>

&example.outputs.similar;

<screen>

<![CDATA[

Argon2i hash: $argon2i$v=19$m=1024,t=2,p=2$YzJBSzV4TUhkMzc3d3laeg$zqU/1IN0/AogfP4cmSJI1vc8lpXRW9/S0sYY2i2jHT0

]]>

</screen>

</example>

</para>

</refsect1>

<refsect1 role="notes">

&reftitle.notes;

<caution>

<para>

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.

</para>

<para>

As noted above, providing the <literal>salt</literal> option in PHP 7.0

will generate a deprecation warning. Support for providing a salt manually

has been removed in PHP 8.0.

</para>

</caution>

<note>

<para>

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 350 milliseconds on interactive systems.

The script in the above example will help you choose a good cost value for your hardware.

</para>

</note>

<note>

<simpara>

Updates to supported algorithms by this function (or changes to the default one) must follow

the following rules:

</simpara>

<para>

<itemizedlist>

<listitem>

<simpara>

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.

</simpara>

</listitem>

<listitem>

<simpara>

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.

</simpara>

</listitem>

</itemizedlist>

</para>

</note>

</refsect1>

<refsect1 role="seealso">

&reftitle.seealso;

<para>

<simplelist>

<member><function>password_verify</function></member>

<member><function>password_needs_rehash</function></member>

<member><function>crypt</function></member>

<member><function>sodium_crypto_pwhash_str</function></member>

</simplelist>

</para>

</refsect1>

</refentry>

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