<?php 
function changeStr($str) 
{	
	// 把字符串分割为数组
    $arr1 = explode('_',$str);
    /**
     * array(3) {
     *  [0]=> string(4) "open" 
     *  [1]=> string(4) "door" 
     *  [2]=> string(2) "ok" }
     */
  	// 遍历数组元素
    foreach($arr1 as $k=>$v) {
    	// 转为首字母大写
        $temp = ucfirst($v);
        // 字符串赋值给数组
        $arr2[] = $temp;
    }
    // 将数组中的元素拼接成字符串
    $str =  implode('',$arr2);
    // 返回拼接后的字符串
    return $str;
}


echo changeStr("open_door");// OpenDoor
echo "<br/>";
echo changeStr("make_by_id");// MakeById