!preg_match for letters not working

i am developing a university project in which !preg_match is not working for letters in FORM it takes both Numbers and Letter, do not giver error here is my code:

<?php
$nameErr = $naErr = $cErr = $yErr =  "";
$id = $name = $color = $year =  "";

if (isset($_POST["submit"])) {

     $id = $_POST["id"];
     $color = $_POST["name"];
      $color = $_POST["color"];
       $year = $_POST["year"];

    if (!preg_match("[0-9]",$id)) 
     {
       $nameErr = "Only number allowed"; 
     }
       else if (!preg_match("~/^[a-zA-Z ]*$/~",$name)) {
       $cErr = "Only letters allowed"; 
     } 

     else if (!preg_match("~/^[a-zA-Z ]*$/~",$color)) {
       $cErr = "Only letters allowed"; 
     } 


  else if  (!preg_match("[0-9]",$year)) {

       $yErr = "Only number allowed"; 
     }
   }
?>