PHP provides an interface for the app to carry parameters and return

function say(){

$test= $_GET["a"];

if (empty($test)) {
$data["result"]=(string) 2; echo json_encode($data);exit;

}else{
$data["result"]=(string) 1;echo json_encode($data);exit;

}

}
say();
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The above introduces the interface provided by PHP for the app to carry parameters and return them, including the content. I hope it will be helpful to friends who are interested in PHP tutorials.