How to convert PascalCase to pascal_case?

Question

If I had:

$string = \"PascalCase\";

I need

\"pascal_case\"

Does PHP offer a function for this purpose?

Answer 1

Not fancy at all but simple and speedy as hell:

function uncamelize($str) 
{
    $str = lcfirst($str);
    $lc = strtolower($str);
    $result = '';
    $length = strlen($str);
    for ($i = 0; $i < $length; $i++) {
        $result .= ($str[$i] == $lc[$i] ? '' : '_') . $lc[$i];
    }
    return $result;
}

echo uncamelize('HelloAWorld'); //hello_a_world

Answer 2

If you are not using Composer for PHP you are wasting your time.

composer require doctrine/inflector

use Doctrine\Inflector\InflectorFactory;

// Couple ways to get class name:

// If inside a parent class
$class_name = get_called_class();

// Or just inside the class
$class_name = get_class();

// Or straight get a class name
$class_name = MyCustomClass::class;

// Or, of course, a string
$class_name = 'App\Libs\MyCustomClass';

// Take the name down to the base name:
$class_name = end(explode('\\', $class_name)));

$inflector = InflectorFactory::create()->build();

$inflector->tableize($class_name); // my_custom_class

https://github.com/doctrine/inflector/blob/master/docs/en/index.rst

Answer 3

Most solutions here feel heavy handed. Here's what I use:

$underscored = strtolower(
    preg_replace(
        ["/([A-Z]+)/", "/_([A-Z]+)([A-Z][a-z])/"], 
        ["_$1", "_$1_$2"], 
        lcfirst($camelCase)
    )
);

"CamelCASE" is converted to "camel_case"

• lcfirst($camelCase) will lower the first character (avoids 'CamelCASE' converted output to start with an underscore)
• [A-Z] finds capital letters
• + will treat every consecutive uppercase as a word (avoids 'CamelCASE' to be converted to camel_C_A_S_E)
• Second pattern and replacement are for ThoseSPECCases -> those_spec_cases instead of those_speccases
• strtolower([…]) turns the output to lowercases

Answer 4

danielstjules/Stringy provieds a method to convert string from camelcase to snakecase.

s('TestUCase')->underscored(); // 'test_u_case'

Answer 5

function camel2snake($name) {
    $str_arr = str_split($name);
    foreach ($str_arr as $k => &$v) {
        if (ord($v) >= 64 && ord($v) <= 90) { // A = 64; Z = 90
            $v = strtolower($v);
            $v = ($k != 0) ? '_'.$v : $v;
        }
    }
    return implode('', $str_arr);
}

Answer 6

Ported from Ruby's String#camelize and String#decamelize.

function decamelize($word) {
  return preg_replace(
    '/(^|[a-z])([A-Z])/e', 
    'strtolower(strlen("\\1") ? "\\1_\\2" : "\\2")',
    $word 
  ); 
}

function camelize($word) { 
  return preg_replace('/(^|_)([a-z])/e', 'strtoupper("\\2")', $word); 
}

One trick the above solutions may have missed is the 'e' modifier which causes preg_replace to evaluate the replacement string as PHP code.