Is there an effective way, maybe with regex, to change the following text pattern?

I have a string like abc_def_ghi_jkl. I want to replace it to AbcDefGhiJkl. I currently use the following code to change it. Is there a more effective way than this?

  • 3
    \$\begingroup\$ What you describe is usually called PascalCase. \$\endgroup\$ Aug 9, 2016 at 8:55

3 Answers 3


More effective solution:

str_replace('_', '', ucwords($key, '_'));

From Gears library

  • 1
    \$\begingroup\$ Hi. Welcome to Code Review! Why is this solution more effective? \$\endgroup\$
    – mdfst13
    May 31, 2016 at 15:23
  • \$\begingroup\$ Because, array_map is expensive operation \$\endgroup\$ Jun 2, 2016 at 12:05
  • 1
    \$\begingroup\$ Here's a test that proves the above point: repl.it/ERrZ/6 (For the lazy: array_map: 575ms, str_replace: 365ms). Suggestion: Add more of an explanation next time :-) \$\endgroup\$ Nov 8, 2016 at 9:58
  • 1
    \$\begingroup\$ Why not str_replace('_', '', ucwords($key, '_'))? It is faster and code shorter by setting delimiter directly in ucwords \$\endgroup\$
    – tom10271
    Feb 23, 2017 at 3:28
  • \$\begingroup\$ @aokaddaoc, good solution! \$\endgroup\$ Jul 14, 2017 at 11:13

I know, its not the latest question, but here is another solution.

Not really pretty, but works well, is in one line and has a better performance than the solution in the question: str_replace(' ', '', ucwords(str_replace(['-', '_'], ' ', $str)))

BTW. here are some microtime results from my server:

// 9.0599060058594E-6
$result = implode('',array_map('ucfirst',explode('_',$string)));

// 4.2915344238281E-5
$result = preg_replace_callback("/(?:^|_)([a-z])/", function($matches) {
  return strtoupper($matches[1]);
}, $string);

// 5.0067901611328E-6
$result = str_replace(' ', '', ucwords(str_replace(['-', '_'], ' ', $string)));

You could use preg_replace_callback(), which replaces matches with the result of a function:

$str = "abc_def_ghi_jkl";
$str = preg_replace_callback("/(?:^|_)([a-z])/", function($matches) {
//       Start or underscore    ^      ^ lowercase character
    return strtoupper($matches[1]);
}, $str);
echo $str;

Whichever works for you, your solution is fine as well.


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