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 class="union"><type>int</type><type>float</type></type><parameter>num</parameter></methodparam>
   <methodparam choice="opt"><type>int</type><parameter>precision</parameter><initializer>0</initializer></methodparam>
   <methodparam choice="opt"><type class="union"><type>int</type><type>RoundingMode</type></type><parameter>mode</parameter><initializer>RoundingMode::HalfAwayFromZero</initializer></methodparam>
  </methodsynopsis>
  <para>
   Returns the rounded value of <parameter>num</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>
  -->
 </refsect1>
 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry>
     <term><parameter>num</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>
      <para>
       If the <parameter>precision</parameter> is positive, <parameter>num</parameter> is
       rounded to <parameter>precision</parameter> significant digits after the decimal point.
      </para>
      <para>
       If the <parameter>precision</parameter> is negative, <parameter>num</parameter> is
       rounded to <parameter>precision</parameter> significant digits before the decimal point,
       i.e. to the nearest multiple of <code>pow(10, -$precision)</code>, e.g. for a
       <parameter>precision</parameter> of -1 <parameter>num</parameter> is rounded to tens,
       for a <parameter>precision</parameter> of -2 to hundreds, etc.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>mode</parameter></term>
     <listitem>
      <para>
       Use <enumname>RoundingMode</enumname> or one of the following constants to specify the mode in which rounding occurs.
       <informaltable>
        <tgroup cols="2">
         <thead>
          <row>
           <entry>&Constants;</entry>
           <entry>&Description;</entry>
          </row>
         </thead>
         <tbody>
          <row>
           <entry><constant>PHP_ROUND_HALF_UP</constant></entry>
           <entry>
            Rounds <parameter>num</parameter> 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>
            Rounds <parameter>num</parameter> 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>
            Rounds <parameter>num</parameter> towards the nearest even value when it is half way
            there, making both 1.5 and 2.5 into 2.
           </entry>
          </row>
          <row>
           <entry><constant>PHP_ROUND_HALF_ODD</constant></entry>
           <entry>
            Rounds <parameter>num</parameter> towards the nearest odd value when it is half way
            there, making 1.5 into 1 and 2.5 into 3.
           </entry>
          </row>
         </tbody>
        </tgroup>
       </informaltable>
       However, please note that some newly added modes only exist in <link linkend="enum.roundingmode">RoundingMode</link>.
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>
 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   The value rounded to the given <parameter>precision</parameter> as a &float;.
  </para>
 </refsect1>

 <refsect1 role="errors">
  &reftitle.errors;
  <simpara>
   The function throws a <exceptionname>ValueError</exceptionname> if <parameter>mode</parameter> is
   invalid.
   Prior to PHP 8.4.0, an invalid mode would silently default to <constant>PHP_ROUND_HALF_UP</constant>.
  </simpara>
 </refsect1>

 <refsect1 role="changelog">
  &reftitle.changelog;
  <informaltable>
   <tgroup cols="2">
    <thead>
     <row>
      <entry>&Version;</entry>
      <entry>&Description;</entry>
     </row>
    </thead>
    <tbody>
     <row>
      <entry>8.4.0</entry>
      <entry>
       Four new rounding modes have been added.
      </entry>
     </row>
     <row>
      <entry>8.4.0</entry>
      <entry>
       Now throws a <exceptionname>ValueError</exceptionname> if
       <parameter>mode</parameter> is invalid.
      </entry>
     </row>
     <row>
      <entry>8.0.0</entry>
      <entry>
       <parameter>num</parameter> no longer accepts internal objects which support
       numeric conversion.
      </entry>
     </row>
    </tbody>
   </tgroup>
  </informaltable>
 </refsect1>

 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title><function>round</function> examples</title>
    <programlisting role="php">
<![CDATA[
<?php
var_dump(round(3.4));
var_dump(round(3.5));
var_dump(round(3.6));
var_dump(round(3.6, 0));
var_dump(round(5.045, 2));
var_dump(round(5.055, 2));
var_dump(round(345, -2));
var_dump(round(345, -3));
var_dump(round(678, -2));
var_dump(round(678, -3));
?>
]]>
    </programlisting>
    &example.outputs;
    <screen role="php">
<![CDATA[
float(3)
float(4)
float(4)
float(4)
float(5.05)
float(5.06)
float(300)
float(0)
float(700)
float(1000)
]]>
    </screen>
   </example>
  </para>
  <para>
   <example>
    <title>How <parameter>precision</parameter> affects a float</title>
    <programlisting role="php">
<![CDATA[
<?php
$number = 135.79;

var_dump(round($number, 3));
var_dump(round($number, 2));
var_dump(round($number, 1));
var_dump(round($number, 0));
var_dump(round($number, -1));
var_dump(round($number, -2));
var_dump(round($number, -3));
?>
]]>
    </programlisting>
    &example.outputs;
    <screen role="php">
<![CDATA[
float(135.79)
float(135.79)
float(135.8)
float(136)
float(140)
float(100)
float(0)
]]>
    </screen>
   </example>
  </para>
  <para>
   <example>
    <title><parameter>mode</parameter> examples</title>
    <programlisting role="php">
<![CDATA[
<?php
echo 'Rounding modes with 9.5' . PHP_EOL;
var_dump(round(9.5, 0, PHP_ROUND_HALF_UP));
var_dump(round(9.5, 0, PHP_ROUND_HALF_DOWN));
var_dump(round(9.5, 0, PHP_ROUND_HALF_EVEN));
var_dump(round(9.5, 0, PHP_ROUND_HALF_ODD));

echo PHP_EOL;
echo 'Rounding modes with 8.5' . PHP_EOL;
var_dump(round(8.5, 0, PHP_ROUND_HALF_UP));
var_dump(round(8.5, 0, PHP_ROUND_HALF_DOWN));
var_dump(round(8.5, 0, PHP_ROUND_HALF_EVEN));
var_dump(round(8.5, 0, PHP_ROUND_HALF_ODD));
?>
]]>
    </programlisting>
    &example.outputs;
    <screen role="php">
<![CDATA[
Rounding modes with 9.5
float(10)
float(9)
float(10)
float(9)

Rounding modes with 8.5
float(9)
float(8)
float(8)
float(9)
]]>
    </screen>
   </example>
  </para>
  <para>
   <example>
    <title><parameter>mode</parameter> with <parameter>precision</parameter> examples</title>
    <programlisting role="php">
<![CDATA[
<?php
echo 'Using PHP_ROUND_HALF_UP with 1 decimal digit precision' . PHP_EOL;
var_dump(round( 1.55, 1, PHP_ROUND_HALF_UP));
var_dump(round(-1.55, 1, PHP_ROUND_HALF_UP));

echo PHP_EOL;
echo 'Using PHP_ROUND_HALF_DOWN with 1 decimal digit precision' . PHP_EOL;
var_dump(round( 1.55, 1, PHP_ROUND_HALF_DOWN));
var_dump(round(-1.55, 1, PHP_ROUND_HALF_DOWN));

echo PHP_EOL;
echo 'Using PHP_ROUND_HALF_EVEN with 1 decimal digit precision' . PHP_EOL;
var_dump(round( 1.55, 1, PHP_ROUND_HALF_EVEN));
var_dump(round(-1.55, 1, PHP_ROUND_HALF_EVEN));

echo PHP_EOL;
echo 'Using PHP_ROUND_HALF_ODD with 1 decimal digit precision' . PHP_EOL;
var_dump(round( 1.55, 1, PHP_ROUND_HALF_ODD));
var_dump(round(-1.55, 1, PHP_ROUND_HALF_ODD));
?>
]]>
    </programlisting>
    &example.outputs;
    <screen role="php">
<![CDATA[
Using PHP_ROUND_HALF_UP with 1 decimal digit precision
float(1.6)
float(-1.6)

Using PHP_ROUND_HALF_DOWN with 1 decimal digit precision
float(1.5)
float(-1.5)

Using PHP_ROUND_HALF_EVEN with 1 decimal digit precision
float(1.6)
float(-1.6)

Using PHP_ROUND_HALF_ODD with 1 decimal digit precision
float(1.5)
float(-1.5)
]]>
    </screen>
   </example>
  <example>
   <title>Example of using <enumname>RoundingMode</enumname></title>
   <programlisting role="php">
<![CDATA[
<?php
foreach (RoundingMode::cases() as $mode) {
    foreach ([
        8.5,
        9.5,
        -3.5,
    ] as $number) {
        printf("%-17s: %+.17g -> %+.17g\n", $mode->name, $number, round($number, 0, $mode));
    }
    echo "\n";
}
?>
]]>
   </programlisting>
   &example.outputs;
   <screen role="php">
<![CDATA[
HalfAwayFromZero : +8.5 -> +9
HalfAwayFromZero : +9.5 -> +10
HalfAwayFromZero : -3.5 -> -4

HalfTowardsZero  : +8.5 -> +8
HalfTowardsZero  : +9.5 -> +9
HalfTowardsZero  : -3.5 -> -3

HalfEven         : +8.5 -> +8
HalfEven         : +9.5 -> +10
HalfEven         : -3.5 -> -4

HalfOdd          : +8.5 -> +9
HalfOdd          : +9.5 -> +9
HalfOdd          : -3.5 -> -3

TowardsZero      : +8.5 -> +8
TowardsZero      : +9.5 -> +9
TowardsZero      : -3.5 -> -3

AwayFromZero     : +8.5 -> +9
AwayFromZero     : +9.5 -> +10
AwayFromZero     : -3.5 -> -4

NegativeInfinity : +8.5 -> +8
NegativeInfinity : +9.5 -> +9
NegativeInfinity : -3.5 -> -4

PositiveInfinity : +8.5 -> +9
PositiveInfinity : +9.5 -> +10
PositiveInfinity : -3.5 -> -3
]]>
   </screen>
  </example>
  </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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