case sensitive preg_replace

MrBodean

I am trying to figure how to use this on case sensitive words where the case is kept the same just the latters changed.

For example
$line = preg_replace("/(h)ello/i","\1owdy", $line);
this will change these 3
hello - howdy
Hello - Howdy
HELLO - Howdy

How can I make it so the HELLO turns to HOWDY

and also what if the replacing letter is not the same
How would I do for example

$line = preg_replace("/(h)ello/i","G'day", $line);

Confused... 🙂

Thanks,
Jeff

bpat1434

I will point you in the directions of RegEx (Regular Expressions) which will help you out.

RegEx Tutorial
RegEx Generator (Use at your own risk)
Our own RegEx Tutorial

~Brett

MrBodean

Brett, whle that answered some questions, it mostly deals with the pattern itself. My problem is trying to figure out what to replace it with.

In the same
$line = preg_replace("/(h)ello/i","\1owdy", $line);

That leaves the first character alone the "H" but what if I want to replace the first character with anohter and match the case?

say replace h with g and H with G

\1 seems to just skip right? How would I determeine to replace upper or lower with a new character?

Thanks,
Jeff

bpat1434

That's out of my league. Sorry.

~Brett

xblue

I don't think there's an easy way (someone please correct me if I'm wrong), but you could try

function matchCase($matches)
{
    $replacement = 'howdie';
    if (ctype_upper($matches[0])){
        return strtoupper($replacement);    

    } else if (ctype_upper(substr($matches[0],0,1))){
        return ucwords($replacement);
    } else {
        return strtolower($replacement);
    } 
}


$input = "Hello hello HELLO HeLLo hEllO";

$output = preg_replace_callback("/hello/i", "matchCase", $input);

echo $output;

As you can see, it only deals with all uppercase, all lowercase or first letter capitalized, ignoring single uppercase letters later within the word, so: feel free to modify & improve.

saraadmin

I'm not sure if it fully fits your requirements, but you can use a character class which will match either lower case 'h' or capital 'H':

"/([hH])ello/\1owdy/i"

thus, "\1" is exactly (case sensitive) the character matched in the original string.

Drakla

You can use a conditional capturing group to do this regex, I just haven't got the time to write it for you, but take a look at this page, set up an OR (?🙁[hH])|([gG])) group for the first letter and work it from there.

http://www.regular-expressions.info/conditional.html