Number after dollar sign in regex

Question

I have found out a code below

<?php $string = 'April 15, 2003'; 
$pattern = '/(\w+) (\d+), (\d+)/i'; 
$replacement = '${1}1,$3';

I just want to know why this 1 after ${1} is declaired and why the value 3 is assigned before the end of the string symbol ?

Probably intent is to get 1st date of the given date. It should have been `$replacement = '${1} 1, $3';` to make it `'April 1, 2003'` — anubhava, Jan 19 '14 at 07:40
@anubhava i think 3 must be given before $ ?..because it act as a string right ? — Avinash Babu, Jan 19 '14 at 07:44
`$3` is probably there for matched group #3 which is 2003 here. — anubhava, Jan 19 '14 at 07:46
You didn't get it. I was also talking about that. If it is written `$11` instead then how does the code know it is `'$1'.'1'` OR `$11`? — anubhava, Jan 19 '14 at 08:09
possible duplicate of [Reference - What does this symbol mean in PHP?](http://stackoverflow.com/questions/3737139/reference-what-does-this-symbol-mean-in-php) — Avinash Babu, May 27 '14 at 06:17

score 3 · Accepted Answer · edited May 23 '17 at 12:23

3

If you execute the code as it is, you get:

April1,2003

This is because you are delimiting the variable $1 to separate it from what would be $11. Here's more on that.

If you change it, you get:

,2003

...because backreference $11 doesn't exist.

Why is $3 declared before the ending string symbol? Because it's part of the preg_replace backreference. If you move it outside of the replacement string, you'll see it crash and burn.

Footnote: why you're replacing this with <variable>1,<variable> seems really odd. That 1 is static - in that it never changes. I'd be more inclined to think you'd want a replacement like ${1}${2},$3 which would return April15,2003.

edited May 23 '17 at 12:23

Community

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answered Jan 19 '14 at 08:51

brandonscript

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can we write ${1}${2},${3} ? – Avinash Babu Jan 19 '14 at 09:23
Sure? No reason to in this case but you can. – brandonscript Jan 19 '14 at 09:25
thanks ..and in a question i have seen http://stackoverflow.com/questions/18027811/preg-replace-add-number-after-backreference something like aeiou ..is aeiuo replaced here ?.. – Avinash Babu Jan 19 '14 at 09:27

Number after dollar sign in regex

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