openssl-random-pseudo-bytes.xml

<?xml version="1.0" encoding="utf-8"?>
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<refentry xml:id="function.openssl-random-pseudo-bytes" xmlns="http://docbook.org/ns/docbook">
 <refnamediv>
  <refname>openssl_random_pseudo_bytes</refname>
  <refpurpose>生成一个伪随机字节串</refpurpose>
 </refnamediv>
 
 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis>
   <type>string</type><methodname>openssl_random_pseudo_bytes</methodname>
   <methodparam><type>int</type><parameter>length</parameter></methodparam>
   <methodparam choice="opt"><type>bool</type><parameter role="reference">strong_result</parameter><initializer>&null;</initializer></methodparam>
  </methodsynopsis>
  <para>
   生成一个伪随机字节串 <type>string</type> ，字节数由 <parameter>length</parameter> 参数指定。 
  </para>
  <para>
   通过 <parameter>strong_result</parameter> 参数可以表示在生成随机字节的过程中是否使用了强加密算法。返回值为 &false; 的情况很少见，但已损坏或老化的有些系统上会出现。
  </para>
 </refsect1>

 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry>
     <term><parameter>length</parameter></term>
     <listitem>
      <para>
       所需字节串的长度，必须为正整数且小于等于 <literal>2147483647</literal>。PHP 会试着将该参数转换为非空整数来使用它。
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>strong_result</parameter></term>
     <listitem>
      <para>
       如果传递到该函数中，将会保存为一个 <type>bool</type> 值来表明是否使用了“强加密”，如果被用于GPG和密码之类的将返回 &true;，否则返回 &false;
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>

 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   返回生成的字节 &string;。
  </para>
 </refsect1>
 
 <refsect1 role="errors">
  &reftitle.errors;
  <para>
   <function>openssl_random_pseudo_bytes</function> 失败时抛出 <classname>Exception</classname>。
  </para>
 </refsect1>

 <refsect1 role="changelog">
  &reftitle.changelog;
  <informaltable>
   <tgroup cols="2">
    <thead>
     <row>
      <entry>&Version;</entry>
      <entry>&Description;</entry>
     </row>
    </thead>
    <tbody>
     <row>
      <entry>8.0.0</entry>
      <entry>
       <parameter>strong_result</parameter> 现在可为 null。
      </entry>
     </row>
     <row>
      <entry>7.4.0</entry>
      <entry>
       此函数失败时不再返回 &false;，而是会抛出 <classname>Exception</classname>。
      </entry>
     </row>
    </tbody>
   </tgroup>
  </informaltable>
 </refsect1>
 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title><function>openssl_random_pseudo_bytes</function> 示例</title>
    <programlisting role="php">
<![CDATA[
<?php
for ($i = 1; $i <= 4; $i++) {
    $bytes = openssl_random_pseudo_bytes($i, $cstrong);
    $hex   = bin2hex($bytes);

    echo "Lengths: Bytes: $i and Hex: " . strlen($hex) . PHP_EOL;
    var_dump($hex);
    var_dump($cstrong);
    echo PHP_EOL;
}
?>
]]>
    </programlisting>
    &example.outputs.similar;
    <screen>
<![CDATA[
Lengths: Bytes: 1 and Hex: 2
string(2) "42"
bool(true)

Lengths: Bytes: 2 and Hex: 4
string(4) "dc6e"
bool(true)

Lengths: Bytes: 3 and Hex: 6
string(6) "288591"
bool(true)

Lengths: Bytes: 4 and Hex: 8
string(8) "ab86d144"
bool(true)

]]>
    </screen>
   </example>
  </para>
 </refsect1>

 <refsect1 role="seealso">
  &reftitle.seealso;
  <simplelist>
   <member><function>random_bytes</function></member>
   <member><function>bin2hex</function></member>
   <member><function>crypt</function></member>
   <member><function>random_int</function></member>
  </simplelist>
 </refsect1>
</refentry>
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