php 老鸟新人 都来看看吧 这个问题有意思
$id1="42022219860323211";<br /> $id2="42022219860323210";<br /> if($id1==$id2){<br /> echo"这两个身份证相同";<br />}else{<br /> echo"这两个身份证不相同";<br /><br />}
理论上是会输出
这两个身份证不相同
但实际输出有点出入
我和另一个同事的 web环境 都是输出 这两个身份证相同
我一个同事 却是正常的 这两个身份证不相同
这两个变量 打印出来 都是 string
是不是php设置哪里不一样?
------解决思路----------------------
那就用===好了
------解决思路----------------------
打印下PHP_INT_MAX 看看两个数字是否超过了php中允许的整型的范围
建议使用===进行比较。
------解决思路----------------------
好像找到原因了了
PHP中的比较运算符有点诡异,很容易出错,现列出比较规则:
1、当两个字符进行大小比较时,是比较着这两个字符的ASCII码大小——这条很容易理解。
2、当两个字符串进行大小比较时,是从第一个字符开始,分别比教对应的ASCII大小,只要从从某个对应位置开始,其中一个字符串的当前位置字符大于另一个字符串对应位置字符,即直接判别出这两个字符串大小,如'ba'>'az'——这条其实大家也都知道的。
那么'10'与'a'比较呢,当然还是一样的啦,首先将'1'和'a'ASCII码进行比较,'a'大。
3、当一个数字与一个字符串/字符进行大小比较时,首先系统尝试将此字符串/字符转换为整型/浮点型,然后进行比较,如'12bsd'转型为12,'a'转型为0,千万需要注意的是此时不是将其对应的ASCII码值与数字进行大小比较了。
其实同样的道理,'a'+10结果也是10。
并且容易忽略的:0 与任意不可转化为数字的字符串比较(操作符为==), 均返回 true。
最后就会出现如下结果:
1 var_dump('1000000'2 var_dump('a'3 var_dump(1
与常规中的思维还是有一点点不同的吧。。

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