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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><type>string</type><parameter>password</parameter></methodparam>
   <methodparam><type>integer</type><parameter>algo</parameter></methodparam>
   <methodparam choice="opt"><type>array</type><parameter>options</parameter></methodparam>
  </methodsynopsis>
  <para>
   <function>password_hash</function> creates a new password hash using a strong one-way hashing
   algorithm. <function>password_hash</function> is compatible with <function>crypt</function>.
   Therefore, password hashes created by <function>crypt</function> can be used with
   <function>password_hash</function>.
  </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 <constant>CRYPT_BLOWFISH</constant> algorithm to
      create the hash. This will produce a standard <function>crypt</function> compatible hash using
      the "$2y$" identifier. The result will always be a 60 character string, &return.falseforfailure;.
     </simpara>
     <para>
      Supported Options:
     </para>
     <itemizedlist>
      <listitem>
       <para>
        <literal>salt</literal> - 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>
      </listitem>
      <listitem>
       <para>
        <literal>cost</literal> - 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>10</literal> will be used. This is a good
        baseline cost, but you may want to consider increasing it depending on your hardware.
       </para>
      </listitem>
     </itemizedlist>
    </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> for the
        <parameter>algo</parameter> parameter, will result
        in the <parameter>password</parameter> 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.
       </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>
     <para>
      If omitted, a random salt will be created and the default cost will be
      used.
     </para>
    </listitem>
   </varlistentry>
  </variablelist>
 </refsect1>

 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   Returns the hashed password, &return.falseforfailure;.
  </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="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)."\n";
?>
]]>
    </programlisting>
    &example.outputs.similar;
    <screen>
<![CDATA[
$2y$10$.vGA1O9wmRjrwAVXD98HNOgsNpDczlqm3Jq7KnEd1rVAGv3Fykk1a
]]>
    </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 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";
?>
]]>
    </programlisting>
    &example.outputs.similar;
    <screen>
<![CDATA[
$2y$12$QjSH496pcT5CEbzjD/vtVeH03tfHKFy36d4J0Ltp3lRtee9HDxY3K
]]>
    </screen>
   </example>
  </para>
  
  <para>
   <example>
    <title><function>password_hash</function> example setting salt manually</title>
    <programlisting role="php">
<![CDATA[
<?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";
?>
]]>
    </programlisting>
    &example.outputs.similar;
    <screen>
<![CDATA[
$2y$11$q5MkhSBtlsJcNEVsYh64a.aCluzHnGog7TQAKVmQwO9C8xb.t89F.
]]>
    </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. 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";
?>
]]>
    </programlisting>
    &example.outputs.similar;
    <screen>
<![CDATA[
Appropriate Cost Found: 11
]]>
    </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>
  </caution>
  <note>
   <para>
    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.
   </para>
  </note>
  <note>
   <simpara>
    Updates to supported algorithms by this function (or changes to the default one) must follow 
    the follwoing 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 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.
      </simpara>
     </listitem>
     <listitem>
      <simpara>
       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.
      </simpara>
     </listitem>
    </itemizedlist>
   </para>
  </note>
 </refsect1>

 <refsect1 role="seealso">
  &reftitle.seealso;
  <para>
   <simplelist>
    <member><function>password_verify</function></member>
    <member><function>crypt</function></member>
    <member><link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="&url.password.compat;">userland implementation</link></member>
   </simplelist>
  </para>
 </refsect1>

</refentry>

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