CODEWITHSUNDEEP
phpregexpreg-match
Kiruba Paul
Kiruba Paul

Reputation: 35

PHP- Regular expression - how to read from Right to left

I have below example 

$game = "hello999hello888hello777last";
preg_match('/hello(.*?)last/', $game, $match);

The above code returns 999hello888hello777, what I need is to retrieve the value just before Last, i.e 777. So I need to read regular expression to read from right to left.

Upvotes: 3

Views: 2510

Answers (4)

Tim Pietzcker
Tim Pietzcker

Reputation: 336208

Your problem is that although .* matches reluctantly, i. e. as few characters as possible, it still starts matching right after hello, and since it matches any characters, it will match right across "boundaries" (last and hello in your case).

Therefore you need to be more explicit about the fact that it's not legal to match across boundaries, and that's what lookahead assertions are for:

preg_match('/hello((?:(?!hello|last).)*)last(?!.*(?:hello|last)/', $game, $match);

Now the match between hello and last is prohibited from containing hello and/or last, and it's not allowed to have hello or last after the match.

Upvotes: 1

PhearOfRayne
PhearOfRayne

Reputation: 5050

This will return the last set of digits before the string last

$game = "hello999hello888hello777last";
preg_match('/hello(\d+)last$/', $game, $match);
print_r($match);

Output Example:

Array
(
    [0] => hello777last
    [1] => 777
)

So you would need $match[1]; for the 777 value

Upvotes: 2

cegfault
cegfault

Reputation: 6632

Why not just reverse the string? Use PHP's strrev and then just reverse your regular expression.

$game = "hello999hello888hello777last";
preg_match('/tsal(.*?)elloh/', strrev($game), $match);

Upvotes: 2

purpletree
purpletree

Reputation: 1943

$game = strrev($game);

How about that? :D

Then just reverse the regular expression ^__^

Upvotes: 4

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