example.php

<?php

$str = 'can_This User createPost';

echo Str::snakeCase($str)."\n";     // can_this_user_create_org
echo Str::camelCase($str)."\n";     // CanThisUserCreateOrg
echo Str::studlyCase($str)."\n";    // canThisUserCreateOrg
echo Str::kebabCase($str)."\n";     // can-this-user-create-org
echo Str::charCase('.', $str)."\n"; // can.this.user.create.org

Str.php

<?php

class Str
{
    public static function split(string $str): array
    {
        $words = preg_split('/(?:(?=[A-Z])|[-_\s])/', $str, -1, PREG_SPLIT_NO_EMPTY);

        return array_map('strtolower', $words);
    }

    public static function charCase(string $glue, string $str): string
    {
        return implode($glue, static::split($str));
    }

    public static function snakeCase(string $str): string
    {
        return static::charCase('_', $str);
    }

    public static function camelCase(string $str): string
    {
        return implode('', array_map('ucwords', static::split($str)));
    }

    public static function studlyCase(string $str): string
    {
        $words = static::split($str);
        $firs = array_shift($words);

        return $firs.implode('', array_map('ucwords', $words));
    }

    public static function kebabCase(string $str): string
    {
        return static::charCase('-', $str);
    }
}