<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<title>Generate a pseudo-random string of bytes</title>
</head>
<body><div class="manualnavbar" style="text-align: center;">
<div class="prev" style="text-align: left; float: left;"><a href="function.openssl-public-encrypt.html">openssl_public_encrypt</a></div>
<div class="next" style="text-align: right; float: right;"><a href="function.openssl-seal.html">openssl_seal</a></div>
<div class="up"><a href="ref.openssl.html">OpenSSL Functions</a></div>
<div class="home"><a href="index.html">PHP Manual</a></div>
</div><hr /><div id="function.openssl-random-pseudo-bytes" class="refentry">
<div class="refnamediv">
<h1 class="refname">openssl_random_pseudo_bytes</h1>
<p class="verinfo">(PHP 5 >= 5.3.0)</p><p class="refpurpose"><span class="refname">openssl_random_pseudo_bytes</span> — <span class="dc-title">Generate a pseudo-random string of bytes</span></p>
</div>
<div class="refsect1 description" id="refsect1-function.openssl-random-pseudo-bytes-description">
<h3 class="title">Description</h3>
<div class="methodsynopsis dc-description">
<span class="type">string</span> <span class="methodname"><strong>openssl_random_pseudo_bytes</strong></span>
( <span class="methodparam"><span class="type">int</span> <code class="parameter">$length</code></span>
[, <span class="methodparam"><span class="type">bool</span> <code class="parameter reference">&$crypto_strong</code></span>
] )</div>
<p class="para rdfs-comment">
Generates a <span class="type"><a href="language.types.string.html" class="type string">string</a></span> of pseudo-random bytes, with the number of bytes
determined by the <em><code class="parameter">length</code></em> parameter.
</p>
<p class="para">
It also indicates if a cryptographically strong algorithm was used to produce the
pseudo-random bytes, and does this via the optional <em><code class="parameter">crypto_strong</code></em>
parameter. It's rare for this to be <strong><code>FALSE</code></strong>, but some systems may be broken or old.
</p>
</div>
<div class="refsect1 parameters" id="refsect1-function.openssl-random-pseudo-bytes-parameters">
<h3 class="title">Parameters</h3>
<p class="para">
<dl>
<dt>
<span class="term"><em><code class="parameter">length</code></em></span>
<dd>
<p class="para">
The length of the desired string of bytes. Must be a positive integer. PHP will
try to cast this parameter to a non-null integer to use it.
</p>
</dd>
</dt>
<dt>
<span class="term"><em><code class="parameter">crypto_strong</code></em></span>
<dd>
<p class="para">
If passed into the function, this will hold a <span class="type"><a href="language.types.boolean.html" class="type boolean">boolean</a></span> value that determines
if the algorithm used was "cryptographically strong", e.g., safe for usage with GPG,
passwords, etc. <strong><code>TRUE</code></strong> if it did, otherwise <strong><code>FALSE</code></strong>
</p>
</dd>
</dt>
</dl>
</p>
</div>
<div class="refsect1 returnvalues" id="refsect1-function.openssl-random-pseudo-bytes-returnvalues">
<h3 class="title">Return Values</h3>
<p class="para">
Returns the generated <span class="type"><a href="language.types.string.html" class="type string">string</a></span> of bytes on success, or <strong><code>FALSE</code></strong> on failure.
</p>
</div>
<div class="refsect1 examples" id="refsect1-function.openssl-random-pseudo-bytes-examples">
<h3 class="title">Examples</h3>
<p class="para">
<div class="example" id="example-868">
<p><strong>Example #1 <span class="function"><strong>openssl_random_pseudo_bytes()</strong></span> example</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /></span><span style="color: #007700">for (</span><span style="color: #0000BB">$i </span><span style="color: #007700">= -</span><span style="color: #0000BB">1</span><span style="color: #007700">; </span><span style="color: #0000BB">$i </span><span style="color: #007700"><= </span><span style="color: #0000BB">4</span><span style="color: #007700">; </span><span style="color: #0000BB">$i</span><span style="color: #007700">++) {<br /> </span><span style="color: #0000BB">$bytes </span><span style="color: #007700">= </span><span style="color: #0000BB">openssl_random_pseudo_bytes</span><span style="color: #007700">(</span><span style="color: #0000BB">$i</span><span style="color: #007700">, </span><span style="color: #0000BB">$cstrong</span><span style="color: #007700">);<br /> </span><span style="color: #0000BB">$hex </span><span style="color: #007700">= </span><span style="color: #0000BB">bin2hex</span><span style="color: #007700">(</span><span style="color: #0000BB">$bytes</span><span style="color: #007700">);<br /><br /> echo </span><span style="color: #DD0000">"Lengths: Bytes: </span><span style="color: #0000BB">$i</span><span style="color: #DD0000"> and Hex: " </span><span style="color: #007700">. </span><span style="color: #0000BB">strlen</span><span style="color: #007700">(</span><span style="color: #0000BB">$hex</span><span style="color: #007700">) . </span><span style="color: #0000BB">PHP_EOL</span><span style="color: #007700">;<br /> </span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$hex</span><span style="color: #007700">);<br /> </span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$cstrong</span><span style="color: #007700">);<br /> echo </span><span style="color: #0000BB">PHP_EOL</span><span style="color: #007700">;<br />}<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
<div class="example-contents"><p>The above example will output
something similar to:</p></div>
<div class="example-contents screen">
<div class="cdata"><pre>
Lengths: Bytes: -1 and Hex: 0
string(0) ""
NULL
Lengths: Bytes: 0 and Hex: 0
string(0) ""
NULL
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)
</pre></div>
</div>
</div>
</p>
</div>
<div class="refsect1 seealso" id="refsect1-function.openssl-random-pseudo-bytes-seealso">
<h3 class="title">See Also</h3>
<ul class="simplelist">
<li class="member"> <span class="function"><a href="function.bin2hex.html" class="function" rel="rdfs-seeAlso">bin2hex()</a> - Convert binary data into hexadecimal representation</span></li>
<li class="member"> <span class="function"><a href="function.crypt.html" class="function" rel="rdfs-seeAlso">crypt()</a> - One-way string hashing</span></li>
<li class="member"> <span class="function"><a href="function.mt-rand.html" class="function" rel="rdfs-seeAlso">mt_rand()</a> - Generate a better random value</span></li>
<li class="member"> <span class="function"><a href="function.uniqid.html" class="function" rel="rdfs-seeAlso">uniqid()</a> - Generate a unique ID</span></li>
</ul>
</div>
</div><hr /><div class="manualnavbar" style="text-align: center;">
<div class="prev" style="text-align: left; float: left;"><a href="function.openssl-public-encrypt.html">openssl_public_encrypt</a></div>
<div class="next" style="text-align: right; float: right;"><a href="function.openssl-seal.html">openssl_seal</a></div>
<div class="up"><a href="ref.openssl.html">OpenSSL Functions</a></div>
<div class="home"><a href="index.html">PHP Manual</a></div>
</div></body></html>
