带有前导零的数字的奇怪行为
我有一些带有一些整数的 PHP 代码并且一切正常，除非我有 08 或 0X 作为整数.当我把它们放在引号中时，一切都很好.
I have some PHP code with some integers and all works fine, except when I have 08 or 0X as integer. It all works fine when I put them in quote.
数字示例:
2 //Works fine
08 //Doesn't work
012 //Doesn't work
"08" //Works fine again
"012" //Works fine again
谁能告诉我背后的原因?
Can anyone tell me the reason behind it?
推荐答案
如果你只是写 08 和 09(不带引号)或任何其他以 0 开头的数字，PHP 认为你正在写一个八进制值，而 08 和09 是无效的八进制数.
If you simply write 08 and 09 (without quotes) or any other numeric with a leading 0, PHP believes you're writing an octal value, and 08 and 09 are invalid octal numbers.
http://www.php.net/manual/en/语言.types.integer.php
语法
整数可以指定为十进制(以 10 为底)、十六进制(以 16 为底)、八进制(以 8 为基数)或二进制(以 2 为基数)表示法，前面可选符号(- 或 +).
Integers can be specified in decimal (base 10), hexadecimal (base 16), octal (base 8) or binary (base 2) notation, optionally preceded by a sign (- or +).
从 PHP 5.4.0 开始提供二进制整数文字.
Binary integer literals are available since PHP 5.4.0.
要使用八进制表示法，请在数字前加上 0(零).使用十六进制表示法 在数字前加上 0x.使用二进制符号 在数字前加上 0b.
To use octal notation, precede the number with a 0 (zero). To use hexadecimal notation precede the number with 0x. To use binary notation precede the number with 0b.
[...]
警告:在 PHP 7 之前，如果在八进制整数(即 8 或 9)中给出了无效数字，则忽略该数字的其余部分.从 PHP 7 开始，会发出解析错误.
Warning: Prior to PHP 7, if an invalid digit was given in an octal integer (i.e. 8 or 9), the rest of the number was ignored. Since PHP 7, a parse error is emitted.
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