title: Eval is discouraged in php 7
body: <p>I am getting formula in string foe example</p>
  
  <pre><code>$a = '1*2*(2+3)';
  echo eval($a) // Output should be 10
  </code></pre>
  
  <p>Now i am trying to evaluate this string and use eval for that but in php 7 give me this error Use of eval() is discouraged so how can i evaluate this string.</p>