Convert array keys from underscore_case to camelCase recursively

Question

I had to come up with a way to convert array keys using undescores (underscore_case) into camelCase. This had to be done recursively since I did not know what arrays will be

Answer 1

Try preg_replace_callback():

$key = preg_replace_callback('/_([a-z]*)/', function($matches) {
    return ucfirst($matches[1]);
}), $key);

A couple notes:

• you only need to look for [a-z] because [A-Z] will already be capitalized
• * 0+ repetition was used in case we have a situation like camel_$case, I assumed that the _ should still be replaced
• here's a demo of the expression that doesn't run the ucfirst() on the first match group