File: ip2long.xml

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<?xml version="1.0" encoding="iso-8859-1"?>
<!-- $Revision: 1.14 $ -->
<!-- splitted from ./en/functions/network.xml, last change in rev 1.18 -->
  <refentry id="function.ip2long">
   <refnamediv>
    <refname>ip2long</refname>
    <refpurpose>
      Converts a string containing an (IPv4) Internet Protocol dotted address
      into a proper address
    </refpurpose> 
   </refnamediv>
   <refsect1>
    <title>Description</title>
     <methodsynopsis>
      <type>int</type><methodname>ip2long</methodname>
      <methodparam><type>string</type><parameter>ip_address</parameter></methodparam>
     </methodsynopsis>
    <para>
     The function <function>ip2long</function> generates an IPv4 Internet
     network address from its Internet standard format (dotted string)
     representation.  If <parameter>ip_address</parameter> is invalid then
     <literal>-1</literal> is returned.  Note that <literal>-1</literal>
     does not evaluate as &false; in PHP.
    </para>
    <note>
     <para>
      As of PHP 5.0.0 <function>ip2long</function> returns &false; when
      <parameter>ip_address</parameter> is invalid.
     </para>
    </note>
    <example>
     <title><function>ip2long</function> Example</title>
     <programlisting role="php">
<![CDATA[
<?php
$ip = gethostbyname('www.example.com');
$out = "The following URLs are equivalent:<br />\n";
$out .= 'http://www.example.com/, http://' . $ip . '/, and http://' . sprintf("%u", ip2long($ip)) . "/<br />\n";
echo $out;
?>
]]>
     </programlisting>
    </example>
    <para>
     <note>
      <para>
       Because PHP's integer type is signed, and many IP addresses will
       result in negative integers, you need to use the "%u" formatter of
       <function>sprintf</function> or <function>printf</function> to get
       the string representation of the unsigned IP address.
      </para>
     </note>
    </para>
    <para>
     This second example shows how to print a converted address with the
     <function>printf</function> function in both PHP 4 and PHP 5:
    </para>
    <example>
     <title>Displaying an IP address</title>
     <programlisting role="php">
<![CDATA[
<?php
$ip   = gethostbyname('www.example.com');
$long = ip2long($ip);

if ($long == -1 || $long === FALSE) {
    echo 'Invalid IP, please try again';
} else {
    echo $ip   . "\n";           // 192.0.34.166
    echo $long . "\n";           // -1073732954
    printf("%u\n", ip2long($ip)); // 3221234342
}
?>
]]>
     </programlisting>
    </example>
    <para>
     <function>ip2long</function> should not be used as the sole form
     of IP validation. Combine it with <function>long2ip</function>:
    </para>
    <example>
     <title>IP validation</title>
     <programlisting role="php">
<![CDATA[
<?php
// make sure IPs are valid. also converts a non-complete IP into
// a proper dotted quad as explained below.
$ip = long2ip(ip2long("127.0.0.1")); // "127.0.0.1"
$ip = long2ip(ip2long("10.0.0")); // "10.0.0.0"
$ip = long2ip(ip2long("10.0.256")); // "10.0.1.0"
?>
]]>
     </programlisting>
    </example>
    <para>
     <function>ip2long</function> will also work with non-complete IP
     addresses. Read <ulink url="&url.ip2long.tech;">&url.ip2long.tech;</ulink>
     for more info.
    </para>
    <note>
     <para>
      <function>ip2long</function> will return &false; for the IP
      <literal>255.255.255.255</literal> in PHP 5 &lt;= 5.0.2. It was fixed in
      PHP 5.0.3 where it returns <literal>-1</literal> (same as PHP 4).
     </para>
    </note>
    <para>
     See also <function>long2ip</function> and
     <function>sprintf</function>.
    </para>
   </refsect1>
  </refentry>

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