PHP缓存机制

display_errors=On
output_buffering=Off
error_reporting= 设置错误级别

ob_start(); //开启缓存
ob_clean(); //清空 outputbuffer的内容
ob_end_clean(); //关闭ob缓存，同时清空
ob_flush(); //输出ob内容，并清空,但不关闭
ob_end_flush(); //把ob缓存的内容输出,并关闭ob
ob_get_contents();  //获取output_buffering的内容

<?php 
ob_start();
echo "abc";
header("content-type:text/html;charset=utf-8");
echo "hello";
ob_clean();
echo "aa";
header("content-type:text/html;charset=utf-8");
?>

<?php 
ob_start();
echo "abc";
header("content-type:text/html;charset=utf-8");
echo "hello";
ob_end_clean();
echo "aa";
header("content-type:text/html;charset=utf-8");
?>

<?php 
ob_start();
echo "abc";
header("content-type:text/html;charset=utf-8");
echo "hello";
ob_flush();
echo "aa";
echo ob_get_contents();
?>

<?php 
ob_start();
echo "abc";
header("content-type:text/html;charset=utf-8");
echo "hello";
ob_end_flush();
echo "aa";
echo ob_get_contents();
?>