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Fix doc bug #63027 (dechex may convert numbers up to PHP_INT_MAX) by clarifying

Browse source 
that PHP treats the parameter as an unsigned int, and working through some of
the implications of that from a userland perspective.


git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@327571 c90b9560-bf6c-de11-be94-00142212c4b1
This commit is contained in:
Adam Harvey 2012-09-10 01:54:11 +00:00
parent 489dde14d5
commit ca01897d64
1 changed files with 40 additions and 5 deletions
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45
reference/math/functions/dechex.xml
View file

@ -12,9 +12,15 @@
<methodparam><type>int</type><parameter>number</parameter></methodparam>
</methodsynopsis>
<para>
Returns a string containing a hexadecimal representation of the
given <parameter>number</parameter> argument. The largest number that can
be converted is 4294967295 in decimal resulting to "ffffffff".
Returns a string containing a hexadecimal representation of the given
unsigned <parameter>number</parameter> argument.
</para>
<para>
The largest number that can be converted is
<constant>PHP_INT_MAX</constant><literal> * 2 + 1</literal> (or
<literal>-1</literal>): on 32-bit platforms, this will be
<literal>4294967295</literal> in decimal, which results in
<function>dechex</function> returning <literal>ffffffff</literal>.
</para>
</refsect1>
<refsect1 role="parameters">
@ -25,7 +31,12 @@
<term><parameter>number</parameter></term>
<listitem>
<para>
Decimal value to convert
The decimal value to convert.
</para>
<para>
As PHP's <type>integer</type> type is signed, but
<function>dechex</function> deals with unsigned integers, negative
integers will be treated as though they were unsigned.
</para>
</listitem>
</varlistentry>
@ -35,7 +46,7 @@
<refsect1 role="returnvalues">
&reftitle.returnvalues;
<para>
Hexadecimal string representation of <parameter>number</parameter>
Hexadecimal string representation of <parameter>number</parameter>.
</para>
</refsect1>
<refsect1 role="examples">
@ -56,6 +67,30 @@ echo dechex(47);
<![CDATA[
a
2f
]]>
</screen>
</example>
</para>
<para>
<example>
<title><function>dechex</function> example with large integers</title>
<programlisting role="php">
<![CDATA[
<?php
// The output below assumes a 32-bit platform.
// Note that the output is the same for all values.
echo dechex(-1)."\n";
echo dechex(PHP_INT_MAX * 2 + 1)."\n";
echo dechex(pow(2, 32) - 1)."\n";
?>
]]>
</programlisting>
&example.outputs;
<screen>
<![CDATA[
ffffffff
ffffffff
ffffffff
]]>
</screen>
</example>