CODEWITHSUNDEEP
phpstringpreg-replace
AndyPerlitch
AndyPerlitch

Reputation: 4729

How do you make preg_replace captures uppercase (php)?

I have a string: 'Some_string_to_capitalize' which I would like to transform to 'Some_String_To_Capitalize'. I have tried:

$result = preg_replace( '/(_([a-z]{1}))/' , strtoupper('$1') , $subject  )

and

$result = preg_replace( '/(_([a-z]{1}))/' , "strtoupper($1)" , $subject  )

I looked at the php man page and here on SO but found nothing. Apologies if this is a dup!

This is the equivalent SO question for Javascript.

Upvotes: 2

Views: 4552

Answers (4)

David Stockton
David Stockton

Reputation: 2251

I think you want to use preg_replace_callback:

In PHP 5.3+

<?php
$subject = 'Some_string_to_capitalize';
$result = preg_replace_callback(
    '/(_([a-z]{1}))/',
    function ($matches) {
        return strtoupper($matches[0]);
    } ,
    $subject
);

For PHP below 5.3

function toUpper($matches) {
    return strtoupper($matches[0]);
}

$result = preg_replace_callback('/(_([a-z]{1}))/', 'toUpper', $subject);

Upvotes: 9

Wil Moore III
Wil Moore III

Reputation: 7194

You've got some good answers posted thus far; however, I thought I'd post a variation just for kicks:

[updated] edited code snipped to be more terse:

<?php

$string = 'Some_strIng_to_caPitÃliZe';
echo mb_convert_case($string, MB_CASE_TITLE, 'UTF-8');
// Some_String_To_Capitãlize

The above code considers the following:

  1. Unicode characters may be a part of the string; in which case, 'UTF-8' should be a safe encoding:

  2. mb_convert_case using the flag MB_CASE_TITLE takes care of words that come in with a mixed case, so we don't need to manually normalize and "_" is considered a word boundry.

  3. The mb_convert_case function works with PHP versions since 4.3.0

PHP Source for reference.

Upvotes: 1

Brian
Brian

Reputation: 3023

I think you want ucfirst not strtoupper. That will capitalize only the first letter of each match, not the entire match like strtoupper will. I'm also thinking you're going to need to switch to preg_replace_callback because your current syntax is telling php to run strtoupper on the string '$1' (which does nothing) and then pass that in as a replacement string to use for ALL matches made. Which would give you the exact same output as input.

Try this instead:

<?php
preg_replace_callback(
    '/(_([a-z]{1}))/',
    create_function(
        // single quotes are essential here,
        // or alternative escape all $ as \$
        '$matches',
        'return ucfirst($matches[0]);'
    ),
    $subject
);
?>

Upvotes: 1

Howard
Howard

Reputation: 39197

Try adding letter "e" (meaning eval) as modifier to your regular expression.

$result = preg_replace("/(_([a-z]{1}))/e" , "strtoupper(\\1)" , $subject);

Upvotes: 1

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