PHP 函数注意

 1.sprintf('%.1f',$str) 诡异啊算是四舍五入吗?

<?php  
  echo  sprintf(&#39;%.1f&#39;,7.52);  // 7.5  
  echo "\n";  
  echo  sprintf(&#39;%.1f&#39;,7.55); // 7.5  
  echo "\n";  
  echo  sprintf(&#39;%.1f&#39;,7.56); // 7.6