How to preg_match for an null (empty) string??
I need something like:
/([0-9]|[NULL STRING])/
+6
A:
You can use ^ to match beginning-of-line, and $ to match end-of-line, thus the regular expression ^$ would match an empty line/string.
Your specific example (a line/string containing a single digit or being empty) would easiest be achieved with ^[0-9]?$.
Mikael Auno
2009-11-27 16:28:07
Or `^\d?$` - somehow I like `\d` than `[0-9]`, sorry :)
Amarghosh
2009-11-27 16:32:24
@Amarghosh: I too prefer `\d`, especially as it is a lot easier/shorter to type. Though, for regular expression beginners, I like to stick with the basics when giving examples as fancy stuff like `\d` doesn't work in all regular expression flavors.
Mikael Auno
2009-11-27 17:15:03
...and `\d` doesn't *mean* the same thing as `[0-9]` in some regex flavors. For instance, in .NET, `\d` matches `٣` (Arabic numeral 3).
Tim Pietzcker
2009-11-27 20:45:10
A:
You can also match a null character with \0. Is that what you meant by [NULL STRING]?
That expression could be /([0-9]|\0)/.
FrustratedWithFormsDesigner
2009-11-27 16:34:25