在
若
下面测试
在测试前为了测试效果更明显，我们在
Output_buffering=off
Display_errors=on
代码
<strong><span 1</span> <span echo</span> "php"<span ;
</span><span 2</span> <span header</span>("content-type:text/html;charset='utf-8'"<span );
</span><span 3</span> <span echo</span> 'ok';</strong>
则会出现
php
Warning: Cannot modify header information - headers already sent by (output started at D:\www\apache\htdocs\test\t2.php:2) in D:\www\apache\htdocs\test\t2.php on line 3
ok
代码2：
<strong><span 1</span> <span ob_start</span><span ();
</span><span 2</span> <span echo</span> "php"<span ;
</span><span 3</span> <span header</span>("content-type:text/html;charset='utf-8'"<span );
</span><span 4</span> <span echo</span> 'ok';</strong>结果就完全正确了
原因分析：
代码Phpecho ‘php’时已经向浏览器发送一个头信息，
当再出现
header("content-type:text/html;charset='utf-8'");
又看到一个头信息，这时已经打回了上面的头信息，无法更该便出错了。
代码‘php’时把要打给浏览器的数据先放到
为加深理解再看以下代码
代码
<strong><span ob_start</span><span ();
</span><span echo</span> "php"<span ;
</span><span header</span>("content-type:text/html;charset='utf-8'"<span );
</span><span echo</span> 'ok'<span ;
</span><span echo</span> '<hr/>'<span ;
</span><span $ob</span>=<span ob_get_contents</span><span ();
</span><span echo</span> <span $ob</span>;</strong>
会输出
Ob_get_contents()
Ob_get_contents()
代码
<strong><span 1</span> <span ob_start</span><span ();
</span><span 2</span> <span echo</span> "php"<span ;
</span><span 3</span> <span ob_clean</span>();<span //</span><span 清除缓存内容但不关闭缓存区，还能用(往里添加东西)</span>
<span 4</span> <span header</span>("content-type:text/html;charset='utf-8'"<span );
</span><span 5</span> <span echo</span> 'ok'<span ;
</span><span 6</span> <span echo</span> '<hr/>'<span ;
</span><span 7</span> <span $ob</span>=<span ob_get_contents</span><span ();
</span><span 8</span> <span echo</span> <span $ob</span>;</strong>结果：
代码
<strong><span ob_start</span><span ();
</span><span echo</span> "php"<span ;
</span><span ob_end_clean</span>();<span //</span><span 清空缓存内容并关闭缓存区，ob_get_contents取不到内容</span>
<span header</span>("content-type:text/html;charset='utf-8'"<span );
</span><span echo</span> 'ok'<span ;
</span><span echo</span> '<hr/>'<span ;
</span><span $ob</span>=<span ob_get_contents</span><span ();
</span><span echo</span> <span $ob</span>;</strong>结果：
代码
<strong><span ob_start</span><span ();
</span><span echo</span> "php"<span ;
</span><span ob_end_flush</span>();<span //</span><span 把缓存送到程序缓存内并关闭ob缓存</span>
<span header</span>("content-type:text/html;charset='utf-8'"<span );
</span><span echo</span> 'ok'<span ;
</span><span echo</span> '<hr/>'<span ;
</span><span $ob</span>=<span ob_get_contents</span><span ();
</span><span echo</span> <span $ob</span>;</strong>
代码
<strong><span ob_start</span><span ();
</span><span echo</span> "php"<span ;
</span><span ob_flush</span>();<span //</span><span 把Ob 缓存送到程序缓存，不关闭ob缓存</span>
<span header</span>("content-type:text/html;charset='utf-8'"<span );
</span><span echo</span> 'ok'<span ;
</span><span echo</span> '<hr/>'<span ;
</span><span $ob</span>=<span ob_get_contents</span><span ();
</span><span echo</span> <span $ob</span>;</strong>
结果：
Ob_clean()
清空
Ob_get_flush()
冲刷出缓存到程序缓存，关闭
代码
<strong><span Ob_start</span><span ();
</span><span echo</span> 'abc'<span ;
</span><span header</span>("content-type:text/html;charset='utf-8'"<span );
</span><span echo</span> 'hello'<span ;
</span><span Ob_flush</span><span ();
</span><span echo</span> 'aa'<span ;
</span><span echo</span> <span ob_get_contents</span><span ();
</span><span //</span><span abchelloaaaa</span></strong>
2.ob_flush(),flush()
代码
<strong><span ob_start</span><span (); </span><span echo</span> 'a'<span ; </span><span flush</span>();<span //</span><span 把Ob缓存冲刷到程序缓存再冲刷到浏览器输出，不影响ob缓存</span> <span echo</span> <span ob_get_contents</span><span (); </span><span //</span><span aa</span></strong>
代码
<strong><span ob_start</span><span (); </span><span echo</span> 'a'<span ; </span><span ob_flush</span>();<span //</span><span 把Ob缓存冲刷到程序缓存,ob里没有了缓存内容</span> <span echo</span> "<br/>ob_con".<span ob_get_contents</span><span (); </span><span //</span><span a 是按正常输出的，Ob里没内容</span></strong>
代码
<strong><span echo</span> <span str_repeat</span>(" ",1024);<span //</span><span 一些版本的 Microsoft Internet Explorer 只有当接受到的256个字节以后才开始显示该页面，所以必须发送一些额外的空格来让这些浏览器显示页面内容。 </span>
<span for</span>(<span $i</span>=0;<span $i</span><5;<span $i</span>++<span ){
</span><span echo</span> <span $i</span><span ;
</span><span echo</span> "<br/>"<span ;
</span><span sleep</span>(1<span );
</span><span flush</span><span ();
}</span></strong>
会一秒输出一个数字
如果没有
