PHP 函數

字符串函數：

數學函數：

      = 123.123456      ();
     (,3);
     (1,10);

數組函數：

      =      (, "Maroon 5");
     (, "Bruno Mars"     (, "Nickelback"     (, "Katy Perry"     (, "Macklemore"      ( 
 
     = ("david","alana","violet","rory"     ();
      (", ", );
     ();