如何在推送内容到php时使用url中的单个字符串var而不是多个？

how do you setup PHP to do use single string in url: ex just ?small instead of the code below

if ( $_GET['api_img_size'] == 'small' ) { ....

but with ?small do the same thing as the code above

Just use isset()

if ( isset( $_GET['small'] ) ) {
  //?small or ?small=1 or ?small=WHATEVER
  // do stuff
}

if ( isset($_GET['small']) ) { ....