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php中自加运算$a++ 与++$a笔记

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Release: 2016-05-26 08:20:17
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想起我们N年前学习php或C语言时发会发对于$a++ 与++$a总是很不了解,不知道是先加一还是循环之后再加一,下面我来给各位详细的介绍一下吧.

这里我们来聊聊PHP的运算符号的升级版: ++,--,呵呵。

++  即自增.

--  即自减.

实际运用:

$a = 10; $a++ = ?  //先用再加,最后结果为11 $a = 10; ++$a = ?  //先加再用,最后结果为11 $a = 10; $b = $a++ + ++$a; echo $a; echo $b;   //算一下吧,结果我回复解答
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来一段例子,来引出重点.

$a = true; echo $a++; echo $a + 1; $b = 'c'; echo $b++; echo $b++;
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上面四个输出你是否知道正确答案呢,下面是总结的一些规律,各位也可以亲自动手实验.

1.布尔型不参与 ++ 运算,不会进行类型转换而参与自增,所以第一个输出是1.

2.布尔型参与算数运算如+,-,会自动进行类型转换,所以第二个输出是2.

3.PHP中字符串++表示升序,所以第三个输出是c,第四个输出是d.


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