floatval.xml

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<refentry xml:id="function.floatval" xmlns="http://docbook.org/ns/docbook">
 <refnamediv>
  <refname>floatval</refname>
  <refpurpose>获取变量的浮点值</refpurpose>
 </refnamediv>
 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis>
   <type>float</type><methodname>floatval</methodname>
   <methodparam><type>mixed</type><parameter>value</parameter></methodparam>
  </methodsynopsis>
  <para>
   获取变量 <parameter>value</parameter> 的 <type>float</type> 值。
  </para>
 </refsect1>
 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry>
     <term><parameter>value</parameter></term>
     <listitem>
      <para>
       可以是任何标量类型。<function>floatval</function> 不能用于对象，这样做会发出
       <constant>E_WARNING</constant> 级别的错误并返回 1。
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>
 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   指定变量的浮点值。空数组返回 0，非空数组返回 1。
  </para>
  <para>
   字符串很可能返回 0，尽管这取决于字符串最左边的字符。适用<link
   linkend="language.types.float.casting">浮点数强制转换</link>的通用规则。
  </para>
 </refsect1>

 <refsect1 role="changelog">
  &reftitle.changelog;
  <informaltable>
   <tgroup cols="2">
    <thead>
     <row>
      <entry>&Version;</entry>
      <entry>&Description;</entry>
     </row>
    </thead>
    <tbody>
     <row>
      <entry>8.0.0</entry>
      <entry>
       对象转换时的错误级别已从 <constant>E_NOTICE</constant> 更改为 <constant>E_WARNING</constant>。
      </entry>
     </row>
    </tbody>
   </tgroup>
  </informaltable>
 </refsect1>

 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title><function>floatval</function> 示例</title>
    <programlisting role="php">
<![CDATA[
<?php
$var = '122.34343The';
$float_value_of_var = floatval($var);
echo $float_value_of_var; // 122.34343
?>
]]>
    </programlisting>
   </example>
  </para>
  <para>
   <example>
    <title><function>floatval</function> 最左边的字符为非数字的示例</title>
    <programlisting role="php">
<![CDATA[
<?php
$var = 'The122.34343';
$float_value_of_var = floatval($var);
echo $float_value_of_var; // 0
?>
]]>
    </programlisting>
   </example>
  </para>
 </refsect1>
 <refsect1 role="seealso">
  &reftitle.seealso;
  <para>
   <simplelist>
    <member><function>boolval</function></member>
    <member><function>intval</function></member>
    <member><function>strval</function></member>
    <member><function>settype</function></member>
    <member><link linkend="language.types.type-juggling">类型转换</link></member>
   </simplelist>
  </para>
 </refsect1>
</refentry>
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