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>interface_exists</H1
><DIV
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NAME="AEN17044"
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><P
>    (PHP 5 &#62;= 5.0.2)</P
>interface_exists&nbsp;--&nbsp;检查接口是否已被定义</DIV
><DIV
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NAME="AEN17047"
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><H2
>说明</H2
>bool <B
CLASS="methodname"
>interface_exists</B
> ( string interface_name [, bool autoload] )<BR
></BR
><P
>&#13;   本函数在由 <CODE
CLASS="parameter"
>interface_name</CODE
>
   给出的接口已定义时返回 <TT
CLASS="constant"
><B
>TRUE</B
></TT
>，否则返回 <TT
CLASS="constant"
><B
>FALSE</B
></TT
>。
  </P
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><P
><B
>例 1. <B
CLASS="function"
>interface_exists()</B
> 例子</B
></P
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><code><font color="#000000">
<font color="#0000BB">&lt;?php<br /></font><font color="#FF8000">// Check the interface exists before trying to use it<br /></font><font color="#007700">if (</font><font color="#0000BB">interface_exists</font><font color="#007700">(</font><font color="#DD0000">'MyInterface'</font><font color="#007700">)) {<br />&nbsp;&nbsp;&nbsp;&nbsp;class </font><font color="#0000BB">MyClass implements MyInterface<br />&nbsp;&nbsp;&nbsp;&nbsp;</font><font color="#007700">{<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</font><font color="#FF8000">// Methods<br />&nbsp;&nbsp;&nbsp;&nbsp;</font><font color="#007700">}<br />}<br /></font><font color="#0000BB">?&gt;</font>
</font>
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  </P
><P
>&#13;   <B
CLASS="function"
>interface_exists()</B
> 默认会尝试调用 <A
HREF="language.oop5.autoload.html"
>__autoload</A
>，如果不希望
   <B
CLASS="function"
>interface_exists()</B
> 去调用 
   <A
HREF="language.oop5.autoload.html"
>__autoload</A
>，可以将 <CODE
CLASS="parameter"
>autoload</CODE
> 参数设为 <TT
CLASS="constant"
><B
>FALSE</B
></TT
>。
  </P
><P
>&#13;   参见 <A
HREF="function.class-exists.html"
><B
CLASS="function"
>class_exists()</B
></A
>。
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