PHP RegEx Replacement With Values From the Original

Question

I am trying to replace a series of plane codes that are strings in PHP.

For example, 757-252 string should become a 752 string

It takes the first two digits before the hypen, and the first digit after the hyphen.

There are three conditions that make this complicated where I can't just use explode and I think need to use RegEx:

The digit before the hyphen may be more than just a single digit, and it MAY be alpha numeric.
The last three digits in the example above is a variable length and can be alpha or numeric.
There are values that DON'T fit this pattern that I need to be left alone (i.e. DHC-8-103)

Any thoughts

RegEx - Working at RegExPal.com

7[0-9][0-9a-zA-Z]+\-[0-9a-z-A-Z][0-9a-zA-Z]+

PHP Attempt to Replace Not Working

$aircraft = '757-252';

$pattern = '/(7)(0-9)(0-9a-zA-Z)+-(0-9a-zA-Z)(0-9a-zA-Z)+/';
$replacement = '\\1\\2\\4';

$aircraft_code = preg_replace($pattern , $replacement , $aircraft);

For starters, you've lost the [ ] brackets from your groups, so they aren't functioning as ranges in character classes like you expect. Instead, you get the literal string "0-9", for example. — Wiseguy
– Wiseguy, Commented Jan 2, 2014 at 1:05
I originally had them as ` [ ] ` and that didn't work either. I saw in other PHP specific examples where there weren't the ` [ ] ` but rather the ` ( ) ` so I thought I'd try that. — Andy Borgmann
– Andy Borgmann, Commented Jan 2, 2014 at 1:20

revo · Accepted Answer · 2014-01-02 12:11:07Z

1

You should check for the beginning of $aircraft value with ^ then capture first 2 digits and the one after hyphen:

^(7\d).+?(\d).*$

And your code:

$aircraft = '757-252';
$pattern = '/^(7\d).+?(\d).*$/';
$replacement = '$1$2';
$aircraft_code = preg_replace($pattern , $replacement , $aircraft);
// echo $aircraft_code; // output: 752

edited Jan 2, 2014 at 12:11

answered Jan 2, 2014 at 11:52

revo

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Comments

Chris · Accepted Answer · 2014-01-02 01:09:36Z

1

Your pattern has changed from the working Regex (missing capture groups), I think your pattern needs to be this:

$pattern = '/(7)([0-9])([0-9a-zA-Z]+)-([0-9a-z-A-Z])([0-9a-zA-Z]+)/';

I'm also a bit rusty at PHP, but I don't think you need to escape the backslashes in your replacement string if you're using '.

edited Jan 2, 2014 at 1:09

answered Jan 2, 2014 at 1:06

Chris

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Comments

Toto · Accepted Answer · 2014-01-03 11:36:19Z

0

I'd use:

$pattern = '/.*\b(7\d)[^-]*-(\w).*/';
$replacement = '$1$2';

edited Jan 3, 2014 at 11:36

answered Jan 2, 2014 at 10:50

Toto

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8 Comments

Toto Over a year ago

@revo: It'll give 75w as expected.

revo Over a year ago

w is not expected as an alphabetical character

Toto Over a year ago

@revo: This must be clarified by OP. For me, it's OK.

revo Over a year ago

It's clarified already first two digits before the hypen, and the first digit after the hyphen.

Toto Over a year ago

@revo: Right, but the second condition says: The last three digits in the example above is a variable length and can be alpha or numeric.

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