title: PHP Notice: Array to string conversion only on PHP 7
body: <p>I am a newbie of PHP. I study it from <code>php.net</code>, but I found a problem today. </p>
  
  <pre><code>class foo {
      var $bar = 'I am bar.';
  }
  
  $foo = new foo();
  $bar = 'bar';
  $baz = array('foo', 'bar', 'baz', 'quux');
  echo "{$foo-&gt;$bar}\n";
  echo "{$foo-&gt;$baz[1]}\n";
  </code></pre>
  
  <p>The documentation(<a href="http://php.net/manual/en/language.types.string.php" rel="noreferrer">http://php.net/manual/en/language.types.string.php</a>) say that the above example will output:</p>
  
  <pre><code>I am bar.
  I am bar.
  </code></pre>
  
  <p>But I get the different output run on my PC(PHP 7):</p>
  
  <pre><code>I am bar.
  &lt;b&gt;Notice&lt;/b&gt;:  Array to string conversion in ... on line &lt;b&gt;9&lt;/b&gt;&lt;br /&gt;
  &lt;b&gt;Notice&lt;/b&gt;:  Undefined property: foo::$Array in ... on line &lt;b&gt;9&lt;/b&gt;&lt;br /&gt;
  </code></pre>
  
  <p>Why?</p>