command line interface - assigning user input to a variable in php -

am building firs php program, problem facing assigning user input variable

here code

<?php printf("enter student test mark"); $test = read_stdin();      function read_stdin() {         $fr=fopen("php://stdin","r");   // open our file pointer read stdin         $input = fgets($fr,128);        // read maximum of 128 characters         $input = rtrim($input);         // trim trailing spaces.         fclose ($fr);                   // close file handle         return $input;                  // return text entered }    printf("enter student assignment mark");  ?> 

how can let user input number , assign test variable

<?php      if(isset($_post['submit'])) {         $test = $_post['marks'];//assigning input value          if(isset($test))         {             $fr=fopen("php://stdin","r");   // open our file pointer read stdin             $input = fgets($fr,128);        // read maximum of 128 characters             $input = rtrim($input);         // trim trailing spaces.             fclose ($fr);                   // close file handle             $result =  $input;              // return text entered         }     }  ?> <form action="#" method="post">     <input type="text" name="marks" placeholder="enter student test mark">     <input type="submit" name="submit" value="submit"> </form>   <?php if(empty($result)) {  } else {   echo ' enter student assignment mark'; } 

or else can show input box first , assign variables , calculations