驼峰

<?php
        //Enter your code here, enjoy!
$name = "my_booool";
$index = strpos($name, '_');
$need_replace =  $name[$index+1];
$result = str_replace('_'.$need_replace, ucfirst($need_replace), $name);
print_r($result);
=============================
$name = "my_booool";
print_r(preg_replace_callback('/_([a-zA-Z])/', function($match){
   return ucfirst($match[1]);
}, $name));