How to convert date to string in php

SimpleDateFormat format1 = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
SimpleDateFormat format2 = new SimpleDateFormat("yyyy年MM月dd日 HH时mm分ss秒");
Date date1 = null;
Date date2 = null;
String str1 = "2009-02-14 12:00:00";
String str2 = "2009年02月14日 12时00分00秒";
// String转Date:String 必须严格按照定义的格式
try {
date1 = format1.parse(str1);
date2 = format2.parse(str2);
} catch (ParseException ex) {
Logger.getLogger(Main.class.getName()).log(Level.SEVERE, null, ex);
}
System.out.println("date1= "+date1);
System.out.println("date2= "+date2);
//Date转StringString
str3 = null;
String str4 = null;
str3 = format1.format(date1);
str4 = format2.format(date2);
System.out.println("str1= "+str3);
System.out.println("str2= "+str4);