enum-exists.xml

<?xml version="1.0" encoding="utf-8"?>
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<refentry xml:id="function.enum-exists" xmlns="http://docbook.org/ns/docbook">
 <refnamediv>
  <refname>enum_exists</refname>
  <refpurpose>检测是否定义对应的枚举</refpurpose>
 </refnamediv>
 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis>
   <type>bool</type><methodname>enum_exists</methodname>
   <methodparam><type>string</type><parameter>enum</parameter></methodparam>
   <methodparam choice="opt"><type>bool</type><parameter>autoload</parameter><initializer>&true;</initializer></methodparam>
  </methodsynopsis>
  <para>
  本函数检测是否定义指定的<link linkend="language.enumerations">枚举</link>。
  </para>
 </refsect1>
 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry>
     <term><parameter>enum</parameter></term>
     <listitem>
      <para>
      枚举的名称。名称的匹配不区分大小写。
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>autoload</parameter></term>
     <listitem>
      <para>
       如果尚未加载，是否<link linkend="language.oop5.autoload">自动加载</link>。
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>
 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
  如果 <parameter>enum</parameter> 已定义，返回 &true;，否则就返回 &false;。
  </para>
 </refsect1>
 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title><function>enum_exists</function> 示例</title>
    <programlisting role="php">
<![CDATA[
<?php
// 在使用之前检测枚举是否存在
if (enum_exists(Suit::class)) {
    $myclass = Suit::Hearts;
}
?>
]]>
    </programlisting>
   </example>
  </para>
 </refsect1>
 <refsect1 role="seealso">
  &reftitle.seealso;
  <para>
   <simplelist>
    <member><function>function_exists</function></member>
    <member><function>class_exists</function></member>
    <member><function>interface_exists</function></member>
    <member><function>get_declared_classes</function></member>
   </simplelist>
  </para>
 </refsect1>
</refentry>
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