PHP正则表达式：或子句不起作用

Question

i need to write a regex for make a double check: if a string contains empty spaces at the beginning, at the end, and if all string it's composed by empty spaces, and if string contains only number. I've write this regex

 $regex = '/^(\s+ )| ^(\d+)$/';

but it doesn't' work. What's wrong ?

Answer 1

The space before ^(\\d+) make your regex can't catch the numeric string.

It should be like below:

$regex = '/^\s*\d*\s*$/';

Answer 2

First if all, remove the space between | and ^. You are trying to match a space before the beginning of the line (^), so that can not work.

I do not exactly understand what you want. Either a string that only consists of white spaces, or a number that may have white spaces at the beginning or end? Try this:

$regex = '/^\s*\d*\s*$/';

Answer 3

First things first: get your spaces right!
For example (\\s+ ) will match a minimum of one space ( \\s+ ) followed by another space ( )! Same applies for the space between | and ^ . This way you will match the space literally every time and this leads to wrong results.

If I get you right and you want to match on strings which

• start with one or more spaces OR
• end with one or more spaces OR
• consist only of spaces OR
• consist only of numbers

I'd use

/^(?:\s+.*|.*\s+$|\d+$)/

Demo @ regex101

This way you match spaces at the start of the string ( \\s+.* ) or ( | ) spaces at the end of the string ( .*\\s+$ ) or a completely numeric string ( \\d+$ ).
Insert capturing groups as needed.

This will match in case the whole string consists of spaces, too, because technically the string then starts with spaces.