1·Just drag up off the keyboard from the letter you need capitalized.
你只需将键盘拖向你要大写的字母即可【略有疑问】。
2·All of the method names are prefixed with get or set and the property names are capitalized.
所有这些方法名都以get或set开头并且属性名都是大写的。
3·First, the expression must match all letters that need to be capitalized.
首先，表达式必须匹配所有需要大写的字母。
4·The API documentation provided with the MQTT client for cleanstart informs developers, rather ominously, in all capitalized bold letters to "USE WITH CARE".
用于 cleanstart 的随 MQTT 客户机一起提供的 API 文档全部采用大写粗体字母（有点威胁性）通知开发人员要“小心使用”。
5·matches[0], in this case, represents the letter that needs to be capitalized. All of this can now be put together using the preg_replace_callback function
$matches[0]在这里代表了需要被大写的字母。