php - search for string in string and replace that

Question

i am asking the question which can be answered by a small attempt in googling but i am not finding anything which can do this, so i am asking here. pls dont downvote and close it, it can be useful for others also:

my problem is: i need to look for some portion of string, and find that and replace that. but my problem is that that portion of string is changing everytime, so i need to inject some regexp.

$url = "www.google.com/test=2";
replace the 'test=2' with 'test=1'
$result = "www.google.com/test=1"

the thing is: the slug can have any number between 1 - 20: test=\d{1,20} this is the case. i tried preg_replace, substr_replace but none of them can do this.

The issue you're facing is you have missed out your delimiters in the preg_replace call — Dale
– Dale, Commented Jan 8, 2013 at 13:48
You match numbers from 0-20 with this regex: regex101.com/r/nI7aI1 — Firas Dib
– Firas Dib, Commented Jan 8, 2013 at 13:54

h2ooooooo · Accepted Answer · 2013-01-08 14:02:59Z

4

I don't see what's wrong with the following /test=\d+/? I think your problem is that you're forgetting the modifiers (in your example: http://codepad.org/ZZNNr1bH, but you have to use modifiers like so: http://codepad.org/9TEkPYJo)

<?php
    $url = "www.google.com/test=2";
    $result = preg_replace("/test=\d+/", "test=1", $url);
    //                      ^        ^
    var_dump($result);
?>

Update:

That said, like Ashley mentioned, \d{1,20} doesn't mean "one to twenty" but rather "any digit character repeated 1 to 20 times".

If you only want digits from 0-20, use the following regex:

/test=([0-9]|1[0-9]|20)/

Basically meaning (a number from 0-9 OR the number 1 FOLLOWED by any number between 0-9 OR the number 20)

It could also be shortened to

/test=(1?\d|20)/

Meaning (1 repeated 1 or 0 times followed by a digit from 0-9 OR the number 20)

edited Jan 8, 2013 at 14:02

answered Jan 8, 2013 at 13:47

h2ooooooo

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Comments

Ashley Sheridan · Accepted Answer · 2013-01-08 13:49:58Z

1

Also, \d{1,20} won't match the numbers between 1 and 20, but 0 and 99,999,999,999,999,999,999 which is not exactly what I think you're after.

answered Jan 8, 2013 at 13:49

Ashley Sheridan

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4 Comments

doniyor Over a year ago

what will it match then? i am not regexp guru

h2ooooooo Over a year ago

@doniyor It will match any digit character (0-9) repeated 1-20 times.

doniyor Over a year ago

oh bad option :). thanks for guidance! so \d+ is the best one here?

h2ooooooo Over a year ago

@doniyor Check my updated response on how to only match 0-20. It's a bit more tricky than you may think. \d+ means "any digit (\d) repeated 1 or more times (+) so it could be indefinitely big.

Rajat Garg · Accepted Answer · 2013-01-08 13:56:57Z

1

$url = "www.google.com/test=2";
$replacement = 1;
echo preg_replace('/(.*test)=([1-20])/', "$1=1" ,$url);

If I understand the question correctly, this should do.

answered Jan 8, 2013 at 13:56

Rajat Garg

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Comments

Matosha · Accepted Answer · 2013-01-08 14:33:41Z

0

$url = "website.com/test=1/asdasd/....";
$check= "test=1";
$newval = "test=2"

if(strstr($url,$check))
  $result = preg_replace($check, $newval, $url);

if the value is contained inside the string, then it can be replaced.

answered Jan 8, 2013 at 14:33

Matosha

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