Regex to fail if a character anywhere before a word but pass if after

Question

I am trying to check a string using regex in PHP. if the string has a character "?" any where before a word then the regex will fail but if "?" is any where after the word then regex will pass. Like, my word is "world" and string is "Hi All? Hello World, How are you". Below are the scenarios.

"Hi? All Hello World, How are you". will fail
"Hi All? Hello World, How are you". will fail
"Hi All Hello? World, How are you". will fail
"Hi All Hello World, How? are you". will pass
"Hi All Hello World, How are? you". will pass
"Hi All Hello World, How are you?". will pass

@TimPietzcker it will pass if there is no "?". I forgot to mention! — Surjyadeb Ganguly, Oct 16 '20 at 15:23
OK, what about `"Hello world, how? are you, world?"` Now we have no `?` before the first `world` but there is one before the second `world`. — Tim Pietzcker, Oct 16 '20 at 15:25
@TimPietzcker string and position of the word is fixed but only the "?" character is changing its position. — Surjyadeb Ganguly, Oct 16 '20 at 15:28

score 0 · Accepted Answer · answered Oct 16 '20 at 15:29

0

If you want to prevent a ? anywhere before any occurrence of world, then a negative lookahead assertion will do the trick:

^(?is)(?!.*\?.*world).*

(?is) turns on case-insensitive matching and allows the dot to match any character including line breaks.

answered Oct 16 '20 at 15:29

Tim Pietzcker

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Regex to fail if a character anywhere before a word but pass if after

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