title: formula for discount
body: <p>What is the formula for discount,</p>
  
  <p>in php is there any default function ,</p>
  
  <p>this is my formula, chk it is correct way ,</p>
  
  <pre><code>  $SELLING_PRICE = $ACTUAL_PRICE-$CHK_DISCOUNT_THERE;
    $PRICE_AFTER_DISCOUNT = $ACTUAL_PRICE-$SELLING_PRICE;
  </code></pre>