PHP read the JS variable ajax code

Title, online looking for a lot of code to see, see the good mess, I tried the next also did not fix. The requirements are very simple, just want to PHP from JS read a formal parameter, and do not need JS to receive what PHP return value, part of the code as follows, ask which God help write A, 3q
$device = $_post[' phone '];
function Count_num ()
{
Echo $device;
}
?>

Reply to discussion (solution)

check.php

!--? phpecho $_post[' phone '];    
 However, you do not receive the check.php processing result code, cannot see 
 
 You can 
 $.post ("check.php", {Phone:device}, function (d) {alert (d)});  
 Look at 
 
 can also 
 file_put_contents (' test.txt ', $_post[' phone ']); 
 Look in Test.txt 
 
 
 
 
 $device = $_post[' phone ']  ;
  
 I thought I would be able to receive it, and the results suggested notice:undefined Index:phone. The 
 above PHP and JS is in the check.php file, I just want to read the JS function in PHP shownumber () The formation of that, and then according to the parameters read in the database to query the satisfied values.  Just want to get a formal parameter, the return value is nothing. 
 you gave me the $.post ("check.php", {Phone:device}, function (d) {alert (d)}); I tried, I didn't respond. 
 
 
 JQ class cited No ? 
 
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