问题
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.
Example numbers:
2 //Works fine
08 //Doesn\'t work
012 //Doesn\'t work
\"08\" //Works fine again
\"012\" //Works fine again
Can anyone tell me the reason behind it?
回答1:
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/language.types.integer.php
Syntax
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 +).
Binary integer literals are available since PHP 5.4.0.
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.
[...]
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.
来源：https://stackoverflow.com/questions/14981133/strange-behaviour-with-numbers-that-have-a-leading-zero