a simple OOP php calculator script. runs only on cli!

gistfile1.php

<?php 


  echo '|------welcome to a function based calculator script----|' ."\n";
menu:

class calc {
   function printf()
{ 
     echo "|----Menu----| ". "\n";
     echo "| 1. + function ". "\n";
     echo "| 2. - function ". "\n";
     echo "| 3. x function ". "\n";
     echo "| 4. % function ". "\n";
     echo "| 5. Exit ". "\n";
 
 }

function add($a,$b)
{ $result = $a + $b;
  echo '|-->result of add(+) function is: '.$result, " \n";
}
function subtract($a,$b)
{ $result = $a - $b;
  echo '|-->result of subtract(-) function is: '.$result, " \n";
}
function multiply($a,$b)
{ $result = $a * $b;
  echo '|-->result of multiply(x) function is: '.$result,  " \n";
}
function divide($a,$b)
{ $result = @($a / $b);
  echo '|-->result of divide(%) function is: '.$result, " \n";
}
function over()
{ exit;
 }
}
$calc = new calc();
$calc->printf();
$option = fwrite(STDOUT," choose function: ");
$option = trim(fgets(STDIN));

if ($option == 1) { 
   $in = fwrite(STDOUT, "|---->enter number 1: ");
   $a = trim(fgets(STDIN));
   $in2 = fwrite(STDOUT, "|---->enter number 2: ");
   $b = trim(fgets(STDIN));
   $calc->add($a,$b);
} elseif 
   ($option == 2) {
   $in = fwrite(STDOUT, "|---->enter number 1: ");
   $a = trim(fgets(STDIN));
   $in2 = fwrite(STDOUT, "|---->enter number 2: ");
   $b = trim(fgets(STDIN));
   $calc->subtract($a,$b);
} elseif
   ($option == 3) {
   $in = fwrite(STDOUT, "|---->enter number 1: ");
   $a = trim(fgets(STDIN));
   $in2 = fwrite(STDOUT, "|---->enter number 2: ");
   $b = trim(fgets(STDIN));
   $calc->multiply($a,$b);
} elseif
   ($option == 4) {
   $in = fwrite(STDOUT, "|---->enter number 1: ");
   $a = trim(fgets(STDIN));
   $in2 = fwrite(STDOUT, "|---->enter number 2: ");
   $b = trim(fgets(STDIN));
   $calc->divide($a,$b);
}  elseif
   ($option == 5) {
   $calc->over();
}  else  echo ' |---->wrong option!!!'."\n";
goto menu 

?>