property-exists.xml

<?xml version="1.0" encoding="utf-8"?>
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<refentry xml:id="function.property-exists" xmlns="http://docbook.org/ns/docbook">
 <refnamediv>
  <refname>property_exists</refname>
  <refpurpose>
   检查对象或类是否具有该属性
  </refpurpose>
 </refnamediv>
 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis>
   <type>bool</type><methodname>property_exists</methodname>
   <methodparam><type class="union"><type>object</type><type>string</type></type><parameter>object_or_class</parameter></methodparam>
   <methodparam><type>string</type><parameter>property</parameter></methodparam>
  </methodsynopsis>
  <para>
   本函数检查给出的 <parameter>property</parameter> 是否存在于指定的类中。
  </para>
  <note>
   <para>
    跟 <function>isset</function> 的区别是即使属性的值为 &null;，<function>property_exists</function> 也会返回 &true;。
   </para>
  </note>
 </refsect1>
 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry>
     <term><parameter>object_or_class</parameter></term>
      <listitem>
       <para>
        需要检查的类名或者类的对象
       </para>
      </listitem>
     </varlistentry>
    <varlistentry>
     <term><parameter>property</parameter></term>
      <listitem>
       <para>
        属性的名称
       </para>
      </listitem>
     </varlistentry>
   </variablelist>
  </para>
 </refsect1>
 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   如果属性存在则返回 &true;，不存在则返回 &false;。
  </para>
 </refsect1>

 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title><function>property_exists</function> 示例</title>
    <programlisting role="php">
<![CDATA[
<?php

class myClass {
    public $mine;
    private $xpto;
    static protected $test;

    static function test() {
        var_dump(property_exists('myClass', 'xpto')); //true
    }
}

var_dump(property_exists('myClass', 'mine'));   //true
var_dump(property_exists(new myClass, 'mine')); //true
var_dump(property_exists('myClass', 'xpto'));   //true
var_dump(property_exists('myClass', 'bar'));    //false
var_dump(property_exists('myClass', 'test'));   //true
myClass::test();

?>
]]>
    </programlisting>
   </example>
  </para>
 </refsect1>

 <refsect1 role="notes">
  &reftitle.notes;
  &note.uses-autoload;
  <note>
   <para>
    <function>property_exists</function> 函数不能检查通过
    <link linkend="language.oop5.overloading.members"><literal>__get</literal></link>
    魔术方法访问的属性。
   </para>
  </note>
 </refsect1>
 
 <refsect1 role="seealso">
  &reftitle.seealso;
  <para>
   <simplelist>
    <member><function>method_exists</function></member>
   </simplelist>
  </para>
 </refsect1>
</refentry>
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