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>章 19. 类与对象（PHP 5）</TD
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> PHP 5 introduces the final keyword, which prevents child classes from
overriding a method by prefixing the definition with final. If the class
itself is being defined final then it cannot be extended.
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>例 19-29. Final methods example</B
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<font color="#0000BB"><?php<br /></font><font color="#007700">class </font><font color="#0000BB">BaseClass </font><font color="#007700">{<br /> </font><font color="#0000BB">public </font><font color="#007700">function </font><font color="#0000BB">test</font><font color="#007700">() {<br /> echo </font><font color="#DD0000">"BaseClass::test() called\n"</font><font color="#007700">;<br /> }<br /> <br /> </font><font color="#0000BB">final public </font><font color="#007700">function </font><font color="#0000BB">moreTesting</font><font color="#007700">() {<br /> echo </font><font color="#DD0000">"BaseClass::moreTesting() called\n"</font><font color="#007700">;<br /> }<br />}<br /><br />class </font><font color="#0000BB">ChildClass </font><font color="#007700">extends </font><font color="#0000BB">BaseClass </font><font color="#007700">{<br /> </font><font color="#0000BB">public </font><font color="#007700">function </font><font color="#0000BB">moreTesting</font><font color="#007700">() {<br /> echo </font><font color="#DD0000">"ChildClass::moreTesting() called\n"</font><font color="#007700">;<br /> }<br />}<br /></font><font color="#FF8000">// Results in Fatal error: Cannot override final method BaseClass::moreTesting()<br /></font><font color="#0000BB">?></font>
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>例 19-30. Final class example</B
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<font color="#0000BB"><?php<br />final </font><font color="#007700">class </font><font color="#0000BB">BaseClass </font><font color="#007700">{<br /> </font><font color="#0000BB">public </font><font color="#007700">function </font><font color="#0000BB">test</font><font color="#007700">() {<br /> echo </font><font color="#DD0000">"BaseClass::test() called\n"</font><font color="#007700">;<br /> }<br /><br /> </font><font color="#FF8000">// Here it doesn't matter if you specify the function as final or not<br /> </font><font color="#0000BB">final public </font><font color="#007700">function </font><font color="#0000BB">moreTesting</font><font color="#007700">() {<br /> echo </font><font color="#DD0000">"BaseClass::moreTesting() called\n"</font><font color="#007700">;<br /> }<br />}<br /><br />class </font><font color="#0000BB">ChildClass </font><font color="#007700">extends </font><font color="#0000BB">BaseClass </font><font color="#007700">{<br />}<br /></font><font color="#FF8000">// Results in Fatal error: Class ChildClass may not inherit from final class (BaseClass)<br /></font><font color="#0000BB">?></font>
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