title: Why is the parameter type of the bcadd method in PHP a string?
body: <p>When I look at the description of <a href="https://www.php.net/manual/en/language.types.float.php#language.types.float" rel="nofollow noreferrer">floating point numbers</a> in the php documentation.
  I get a warning like this:
  <img src="https://raw.githubusercontent.com/lightWey/notebook/master/imageHost/2019/07/4.png" alt="pic-1"></p>
  
  <p>I clicked on the link about <a href="https://www.php.net/manual/en/book.bc.php" rel="nofollow noreferrer">arbitrary precision math functions</a> because I need higher precision, then I got bcadd methoad.</p>
  
  <pre class="lang-php prettyprint-override"><code>echo floor((0.1+0.7)*10);
  //result : 7
  
  echo floor(bcadd(0.1+0.7)*10);
  //result : 8
  </code></pre>
  
  <p>It works, but I noticed that the parameter type of the bcadd method is a string.</p>
  
  <p><img src="https://raw.githubusercontent.com/lightWey/notebook/master/imageHost/2019/07/5.png" alt="pic-2"></p>
  
  <p>I just don't understand why a parameter type is a string as a math function.
  Any opinion would be greatly appreciated...</p>