Hi, I'm Derick, and this is PHP internals news, a weekly podcast dedicated to demystifying the development of the PHP language. This is Episode 62. Today I'm talking with George Peter Banyard about an RFC that he's proposing called saner numeric strings. Hello George, how are you this morning?

How are you; I'm doing fine. I'm George Peter Banyard. I work on PHP, and I'm currently employed by The Coding Machine to work on PHP.

I actually think I have a bug swatter from The Coding Machine, which is hilarious. Huh, I can't show you that okay of course in a podcast and not on TV. But yes, I think I got it in Paris at some point at a conference there, and it's been happily getting rid of flies in my living room. Anyway, that's not what we want to talk about here today, we want to talk about the RFC that is made, what is the problem that is RFC is hoping to address?

PHP has the concept of numeric strings, which are strings which have like integers or floats encoded as a string. Mostly that would arrive when you have like a get request or post request and you take like the value of a form, which would be in a string. Issue is that PHP makes some kind of weird distinctions, and classifies numeric strings in three different categories mainly. So there are purely numeric strings, which are pure integers or pure floats, which can have an optional leading whitespace and no trailing whitespace.

Does that also include like exponential numbers in there?

Yes. However trailing white spaces are not part of the numeric string specification in the PHP language. To deal with that PHP has a concept of leading numeric strings, which are strings which are numeric but like in the first few bytes, so it can be leading whitespace, integer or float, and then it can be whatever else afterwards, so it can be characters, it can be any white spaces, that will consider as a leading numeric string. The distinction is important because PHP will sometimes only accept pure numeric strings. But in some other place where we'll accept leading numeric strings. Of casts will accept whatever string possible and will try to coerce it into an integer. In weak mode, if you have a type hint. It will accept leading numeric strings, and it will emit an e_notice that a non well formed string has been encountered. When you use like a purely string string, you'll get a non numeric string encountered warning. So the main issue with that is that like strings which have a leading whitespace are considered more numeric by PHP than strings with trailing whitespaces. It is a pretty odd distinction to make.

For me to get this right, the numeric string in PHP can have whitespace at the start, and then have numbers. There's a leading numeric string that can have optional whitespace in front, numbers and digits, and then rubbish. Then there's a non numeric string which never has any numbers in it.