Initialize the current platform

$plat=!empty($_GET['P'])?$_GET['P']:"front"; Distinguish between front and back. Use P to divide front and back. The initialization default value is front.

? : It is the ternary operator $plat=!empty($_GET['P'])?$_GET['P']:"front"; which means if $_GET['P'] has a value, no If it is empty, assign it to $plat. If $_GET['P'] is empty, assign 'front' to $plat.