Regex Help

Baving

Hi,

I am trying to match the string:

{L_***}

With the *** being [A-Za-z0-9_]

I have the following regex:

preg_match("/(L\_[A-Za-z0-9_-]+)/",'Replacemement',$string);

But it doesn't seem to work..

Does anyone know what it should be?

Thanks!

laserlight

Due to the "replacement" thing, it sounds like you are getting [man]preg_match/man and [man]preg_replace/man mixed up. You probably meant to write:

preg_match('/L\_[A-Za-z0-9_-]+/', $string)

Note that you have an extra dash at the end of the character class. Are you sure you want to include the dash?

Baving

Sorry! I meant preg_replace instead of preg_match.

laserlight

Well, it seems to work for me:

<?php
$subject = 'This is a weird string with a {L_123Avenue} and another {L_sub-string}.';
$replacement = 'replacement';

$subject = preg_replace('/L\_[A-Za-z0-9_-]+/', $replacement, $subject);
echo $subject;
?>

nrg_alpha

do you mean something like this?

$str = "this is a {L_tESTing12-3} test";
echo $str . '<br />';
$str = preg_replace('#{L[\w-]+}#', '', $str);
echo $str;

EDIT:
If you don't want the { } curlybrace characters, you can simply substitute the expression with:

$str = preg_replace('#L[\w-]+#', '', $str);

nrg_alpha

Sorry.. I did find a problem with my expression.. this one should do it:

$str = preg_replace('#L[\w-]+(?=})#', '', $str);

laserlight

If you don't want the { } curlybrace characters, you can simply substitute the expression with:

Yes, you need to be very clear with what you want. According to your original specifications, the correct code would actually be:

$string = preg_replace('/{L_\w}/', $replacement, $string);

Though I expect that you intended:

$string = preg_replace('/{L_\w+}/', $replacement, $string);

nrg_alpha

Indeed... but the original post is confusing.. the characters asked for is a-zA-Z0-9_ (which perfectly defines \w... but then in the first post expression snippet, there is a dash there '-'.. so I'm not sure if this is also supposed to be included in the match or not (so my last example assumes that the dash is also looked for).

Given the OP's first example, it appears the curly braces are meant to stay? (as they are not included in the expresison).

laserlight

nrg_alpha wrote:
Sorry.. I did find a problem with my expression.. this one should do it:

It would also replace a substring that is not preceded by a {. Frankly, the easiest solution in such a case is:

$subject = preg_replace('/{L_[\w-]+}/', '{' . $replacement . '}', $subject);

nrg_alpha wrote:
Indeed... but the original post is confusing.

Don't worry, my comment was directed at Baving, not you.

Baving

Hi,

Sorry for not making it clear in my original post.

I have this array:

$array=array('l_hello'=>'Hello','l_bye'=>'Bye');

In a file there is a phrase, this is shown as {L_***} so.. {L_hello}.

I need a piece of code to check for matches to {L_} and replace the matched value of with the appropriate array value.

laserlight

You need to be clear, and this includes even the letter case of your examples.

Let's examine your newly stated requirements:
1. You have this array: $array=array('l_hello'=>'Hello','l_bye'=>'Bye');
2. In a file there is a phrase, this is shown as {L} so.. {L_hello}.
3. Check for matches to {L} and replace the matched value of *** with the appropriate array value.

This means that if the file contains the string '{L_hello}', after the processing it would contain '{L_hello}'. Surprised? Well, this is because 'L_hello' does not match anything in the array.

Okay, so maybe you change the array to:
$array=array('L_hello'=>'Hello','L_bye'=>'Bye');

So we do the processing again... and now the result is '{L_Hello}'. As stated, the script matched {L_***}, and then replaced the asterisked portion with the appropriate array value, namely 'Hello'. Is this really what you want?

Baving

That is exactly what I want, is it not possible to turn the L into lowercase? It is just all the current array values and throughout the system have lower L's

laserlight

Ah. Yes, it is possible to account for the case. Exactly how depends on your requirements. For example, is the array guaranteed to only have keys that begin with 'l'? If so, then it may be easier to hard code the 'L' and strip out the 'l_' from the keys of the array. If not, then perhaps the keys could be changed such that the first letter is converted to uppercase.

More interestingly, are all the keys of the array going to consist of a prefix followed by a word, and then would the value be the same word, but capitalised? If so, then the processing could actually be done without an array for lookup 🙂

nrg_alpha

Baving.. are you basically saying you only want to change the uppercase L to lowercase l?
If so , it would have been easier to ask for this from the getgo.

IF I understand you correctly:

$phrase = '{L_hello}';
echo $phrase . '<br />';
$phrase = preg_replace('#{L_#', '{l_', $phrase);
echo $phrase;

May I offer some good advice for future requests? Be aware that your thought processes in accomplishing a certain task may be flawed (I mean no offense by this.. my thought processes are flawed more often than not).. So instead of jumping though hoops by illustrating a potentially flawed thought process, just cut to the chase and ask..

I have a phrase such as {L_Hello}.. I need to put that L into lower case.
Remember that regex is a very concise language that offers no wiggle room. You must be absolutely positively clear in what you are asking for..

perhaps posting a simple set of before and after examples:
before:
{L_Hello}

After:
{l_Hello}

Makes things MUCH more clear for everyone trying to help. Sorry, I'm not giving you hell. I just want you to understand that unless you are crystal clear, there will be many unecessary rounds of confusion.

Cheers,

NRG

laserlight

are you basically saying you only want to change the uppercase L to lowercase l?

It sounds like the lower case and uppercase L thing is merely a limitation of what is currently in the system. Of course, if one really was just going to change '{L' to '{l}', then str_replace() would be good enough.

nrg_alpha

Good point. I keep losing sight of when regex or str_replace is best.