CaseConverter an static class for conversions betweenn camelCase <--> StudlyCase <--> snake_case.

CaseConverter.php

<?php

/**
 * Class CaseConverter
 *
 * Library for camelCase/StudlyCase/snake_case conversions.
 */
class CaseConverter {

  /**
   * snake_case to camelCase
   *
   * @param string $str
   * @return string
   */
  static function snakeToCamel($str) {
    return lcfirst(str_replace(' ', '', ucwords(str_replace('_', ' ', $str))));
  }

  /**
   * snake_case to StudlyCaps
   *
   * @param string $str
   * @return string
   */
  static function snakeToStudly($str)  {
    return str_replace(' ', '', ucwords(str_replace('_', ' ', $str)));
  }

  /**
   * camelCase to StudlyCaps
   *
   * @param string $str
   * @return string
   */
  static function camelToStudly($str)  {
    return ucfirst($str);
  }

  /**
   * StudlyCaps to camelCase
   *
   * @param string $str
   * @return string
   */
  static function studlyToCamel($str)  {
    return lcfirst($str);
  }

  /**
   * camelCase and StudlyCaps to snake_case
   *
   * @param string $str
   * @return string
   */
  static function camelToSnake($str) {
    // Easy but slow implementation:
    // return strtolower(preg_replace('/([a-z])([A-Z])/', '$1_$2', $str));

    // Fast implementation without slow regex replace:
    // Inspired by http://stackoverflow.com/a/1589544/807647
    // Lowercase first letter.
    $str[0] = strtolower($str[0]);
    $len = strlen($str);
    for ($i = 0; $i < $len; ++$i) {
      // See if we have an uppercase character and replace; ord A = 65, Z = 90.
      if (ord($str[$i]) > 64 && ord($str[$i]) < 91) {
        // Replace uppercase of with underscore and lowercase.
        $replace = '_' . strtolower($str[$i]);
        $str = substr_replace($str, $replace, $i, 1);
        // Increase length of class and position since we made the string longer.
        ++$len;
        ++$i;
      }
    }

    return $str;
  }

  /**
   * camelCase and StudlyCaps to snake_case
   *
   * @param string $str
   * @return string
   */
  static function studlyToSnake($str) {
    return self::camelToSnake($str);
  }

}