iis7下，php如何显示错误

display_errors = on;
error_reporting = E_ALL & ~E_NOTICE;

<?xml version="1.0" encoding="UTF-8"?>
<!--
  For more information on how to configure your ASP.NET application, please visit
 
http://go.microsoft.com/fwlink/?LinkId=169433
 
  -->
<configuration>
  <system.web>
    <compilation debug="true" targetFramework="4.5"/>
    <httpRuntime targetFramework="4.5"/>
  </system.web>
  <system.webServer>
    <httpErrors errorMode="DetailedLocalOnly" existingResponse="PassThrough"></httpErrors>
  </system.webServer>
</configuration>