round.xml

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<!-- $Revision$ -->
<refentry xml:id="function.round" xmlns="http://docbook.org/ns/docbook">
 <refnamediv>
  <refname>round</refname>
  <refpurpose>Rounds a float</refpurpose>
 </refnamediv>
 <refsect1 role="description">
  &reftitle.description;
   <methodsynopsis>
    <type>float</type><methodname>round</methodname>
    <methodparam><type>float</type><parameter>val</parameter></methodparam>
    <methodparam choice="opt"><type>int</type><parameter>precision</parameter><initializer>0</initializer></methodparam>
    <methodparam choice="opt"><type>int</type><parameter>mode</parameter><initializer>PHP_ROUND_HALF_UP</initializer></methodparam>
   </methodsynopsis>
  <para>
   Returns the rounded value of <parameter>val</parameter> to
   specified <parameter>precision</parameter>
   (number of digits after the decimal point).
   <parameter>precision</parameter> can also be negative or zero (default).
  </para>
  <!-- It's not true
  <para>
   <caution>
    <simpara>
     When rounding on exact halves <function>round</function> rounds down on
     evens and up on odds.  If you want to always force it in one direction
     on a .5 (or .05 in your case) add or subtract a tiny fuzz factor.  The
     reason behind rounding half the values down and the other half up is to
     avoid the classical banking problem where if you always rounded down
     you would be stealing money from your customers, or if you always
     rounded up you would end up over time losing money.  By averaging it
     out through evens and odds you statistically break even.
    </simpara>
   </caution>
  </para>
  -->
  <para>
   <note>
    <simpara>
     PHP doesn't handle strings like <literal>"12,300.2"</literal> correctly
     by default. See <link linkend="language.types.string.conversion"
     >converting from strings</link>.
    </simpara>
   </note>
  </para>
 </refsect1>
 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry>
     <term><parameter>val</parameter></term>
     <listitem>
      <para>
       The value to round
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>precision</parameter></term>
     <listitem>
      <para>
       The optional number of decimal digits to round to.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>mode</parameter></term>
     <listitem>
      <para>
       Use one of the following constants to specify the mode in which rounding occurs.
       <informaltable>
        <tgroup cols="2">
         <thead>
          <row>
           <entry>Constant</entry>
           <entry>&Description;</entry>
          </row>
         </thead>
         <tbody>
          <row>
           <entry><constant>PHP_ROUND_HALF_UP</constant></entry>
           <entry>
            Round <parameter>val</parameter> up to <parameter>precision</parameter> decimal places
            away from zero, when it is half way there. Making 1.5 into 2 and -1.5 into -2.
           </entry>
          </row>
          <row>
           <entry><constant>PHP_ROUND_HALF_DOWN</constant></entry>
           <entry>
            Round <parameter>val</parameter> down to <parameter>precision</parameter> decimal places
            towards zero, when it is half way there. Making 1.5 into 1 and -1.5 into -1.
           </entry>
          </row>
          <row>
           <entry><constant>PHP_ROUND_HALF_EVEN</constant></entry>
           <entry>
            Round <parameter>val</parameter> to <parameter>precision</parameter> decimal places
            towards the next even value.
           </entry>
          </row>
          <row>
           <entry><constant>PHP_ROUND_HALF_ODD</constant></entry>
           <entry>
            Round <parameter>val</parameter> to <parameter>precision</parameter> decimal places
            towards the next odd value.      
           </entry>
          </row>
         </tbody>
        </tgroup>
       </informaltable>
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>
 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   The rounded value
  </para>
 </refsect1>
 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title><function>round</function> examples</title>
    <programlisting role="php">
<![CDATA[
<?php
echo round(3.4);         // 3
echo round(3.5);         // 4
echo round(3.6);         // 4
echo round(3.6, 0);      // 4
echo round(1.95583, 2);  // 1.96
echo round(1241757, -3); // 1242000
echo round(5.045, 2);    // 5.05
echo round(5.055, 2);    // 5.06
?>
]]>
    </programlisting>
   </example>
  </para>
  <para>
   <example>
    <title><parameter>mode</parameter> examples</title>
    <programlisting role="php">
<![CDATA[
<?php
echo round(9.5, 0, PHP_ROUND_HALF_UP);   // 10
echo round(9.5, 0, PHP_ROUND_HALF_DOWN); // 9
echo round(9.5, 0, PHP_ROUND_HALF_EVEN); // 10
echo round(9.5, 0, PHP_ROUND_HALF_ODD);  // 9

echo round(8.5, 0, PHP_ROUND_HALF_UP);   // 9
echo round(8.5, 0, PHP_ROUND_HALF_DOWN); // 8
echo round(8.5, 0, PHP_ROUND_HALF_EVEN); // 8
echo round(8.5, 0, PHP_ROUND_HALF_ODD);  // 9
?>
]]>
    </programlisting>
   </example>
   <example>
    <title><parameter>mode</parameter> with precision examples</title>
    <programlisting role="php">
<![CDATA[
<?php
/* Using PHP_ROUND_HALF_UP with 1 decimal digit precision */
echo round( 1.55, 1, PHP_ROUND_HALF_UP);   //  1.6
echo round( 1.54, 1, PHP_ROUND_HALF_UP);   //  1.5
echo round(-1.55, 1, PHP_ROUND_HALF_UP);   // -1.6
echo round(-1.54, 1, PHP_ROUND_HALF_UP);   // -1.5

/* Using PHP_ROUND_HALF_DOWN with 1 decimal digit precision */
echo round( 1.55, 1, PHP_ROUND_HALF_DOWN); //  1.5
echo round( 1.54, 1, PHP_ROUND_HALF_DOWN); //  1.5
echo round(-1.55, 1, PHP_ROUND_HALF_DOWN); // -1.5
echo round(-1.54, 1, PHP_ROUND_HALF_DOWN); // -1.5

/* Using PHP_ROUND_HALF_EVEN with 1 decimal digit precision */
echo round( 1.55, 1, PHP_ROUND_HALF_EVEN); //  1.6
echo round( 1.54, 1, PHP_ROUND_HALF_EVEN); //  1.5
echo round(-1.55, 1, PHP_ROUND_HALF_EVEN); // -1.6
echo round(-1.54, 1, PHP_ROUND_HALF_EVEN); // -1.5

/* Using PHP_ROUND_HALF_ODD with 1 decimal digit precision */
echo round( 1.55, 1, PHP_ROUND_HALF_ODD);  //  1.5
echo round( 1.54, 1, PHP_ROUND_HALF_ODD);  //  1.5
echo round(-1.55, 1, PHP_ROUND_HALF_ODD);  // -1.5
echo round(-1.54, 1, PHP_ROUND_HALF_ODD);  // -1.5
?>
]]>
    </programlisting>
   </example>
  </para>
 </refsect1>
 <refsect1 role="changelog">
  &reftitle.changelog;
  <para>
   <informaltable>
    <tgroup cols="2">
     <thead>
      <row>
       <entry>&Version;</entry>
       <entry>&Description;</entry>
      </row>
     </thead>
     <tbody>
      <row>
       <entry>5.3.0</entry>
       <entry>
        The <parameter>mode</parameter> parameter was introduced.
       </entry>
      </row>
      <row>
       <entry>5.2.7</entry>
       <entry>
        The inner workings of <function>round</function> was changed 
        to conform to the C99 standard.
       </entry>
      </row>
     </tbody>
    </tgroup>
   </informaltable>
  </para>
 </refsect1>

 <refsect1 role="seealso">
  &reftitle.seealso;
  <para>
   <simplelist>
    <member><function>ceil</function></member>
    <member><function>floor</function></member>
    <member><function>number_format</function></member>
   </simplelist>
  </para>
 </refsect1>
</refentry>

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