PHP变量及其检查null与某些规则

i want some hints for php

Here is my variables like this

$error;
$a=$_POST["sdf"];
$b=$_POST["dsf"];
$c=$_POST["ssdfsdfdf"];
$d=$_POST["ssdfsddf"];
$e=$_POST["sdfsdfdf"];
$f=$_POST["sfsdfsdf"];
$g=$_POST["sdsdff"];
$g=$_POST["sdsdfsdff"];

I want to check whether those variables are empty or not and dispaly message like this

if(empty($a)){
$error.="Hey you missed the $a "; // $a value
}

now i have to repeat all those codes ...

Imagine i have more than 40 variables can i get some hints to short that code

i tried switch statement but it's not working ..i want to display all error message of anyone variable is missing...

Regards

$required = ["sdf", "dsf", "ssdfsdfdf"]; //etc. etc.
$arr = [];
//Loop through and santize input. 
foreach($_POST as $key => $value)
{
    //sanitize input here

    //store in array
    $arr[$key] = $value; 
}

//check empty
foreach($arr as $key => $value)
{
    if(in_array($key, $required)
    {
       if(empty($value))
       { 
           throw new Exception("One of the required attributes is empty"); 
       }
    }
}

Don't assign to a variable. You can process the POST array directly

foreach($_POST as $value) {
if(is_array($value)) {
    foreach($value as $val) {
       if(empty($val)){
          $error.="Hey you missed the $val "; // $a value
       }
    }
} else {
     if(empty($value)){
          $error.="Hey you missed the $value "; // $a value
     }
}
}

If you want to check all POST variables in the page try using foreach like this

foreach($_POST as $key=>$values)
{
if($values == "")
echo "Hey you missed out ".$key;
}

Note: Use sensible naming in key(POST variables) so that it helps in displaying message