PHP regex change dependent on string

Question

I have a String like so

2*O#QR   4 F0 P0 A0 J4 C2 D0 I0 Y9 LHRDOH 1505 2345      388 0E

And to get the data I require I have the following regex

^(\d)+[^#$]*[#$](?'code1'\p{Lu}{2})\s*(?'code2'\d{1,4})\b\s*(?<seat1>[A-Z][0-9.](?:\s+[A-Z][0-9.])*+)\s+(?<from>[A-Z]{3})(?<to>[A-Z]{3})\s+(?<other>.*\S)\s*

The problem is that the regex I am using obtains the airline code, seats, from, to and other information. So for the above string it would look something like

1. `2`
code1 `QR`
code2 `4`
seat1 `F0 P0 A0 J4 C2 D0 I0 Y9`
from `LHR`
to `DOH`
other `1505 2345 388 0E`

Sometimes however I get a string like the following which the regex will fail on

3*O#QR 904 J4 C2 D0 I0 Y9 B9 H9 K9    MEL 0055 2125 #1   77W 0E

The difference in the above string is there is no from, only a to (MEL). Is there any way of changing my regex to only look for from and to if they are both present? If not, just look for to?

Thanks

Please try to rephrase your question to explain exactly what you mean. Often, you can actually solve it yourself if you try to do that. In this case, think in the lines of 'What am I actually (exactly) trying to match with this regular expression?' — Erik S
– Erik S, Commented Mar 26, 2015 at 22:43
I have rephrased it so hopefully it is clearer. I have a feeling I need a question mark in the regex but not 100% sure — Nick Price
– Nick Price, Commented Mar 26, 2015 at 22:52
oh, think I solved it by adding a ? after the from brackets, thanks — Nick Price
– Nick Price, Commented Mar 26, 2015 at 22:53

cwurtz · Accepted Answer · 2015-03-26 22:55:28Z

2

The problem is this part of your regex

(?<to>[A-Z]{3})\s+(?<other>.*\S)

It requires you have something that matches (?<to>[A-Z]{3}) prior to a space. If you change this part of it to be

(?<to>[A-Z]{3})?\s+(?<other>.*\S)

That is, adding a ? after (?<to>[A-Z]{3}) and before \s

It will tell the regex to expect zero or more of that pattern.

Making your final working pattern

^(\d)+[^#$]*[#$](?'code1'\p{Lu}{2})\s*(?'code2'\d{1,4})\b\s*(?<seat1>[A-Z][0-9.](?:\s+[A-Z][0-9.])*+)\s+(?<from>[A-Z]{3})(?<to>[A-Z]{3})?\s+(?<other>.*\S)\s*

I hope that made sense

answered Mar 26, 2015 at 22:55

cwurtz

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1 Comment

Nick Price Over a year ago

Literally figured it out seconds before you posted this. Thanks for the help

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