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PHP怎么即时输出结果到浏览器

Jun 20, 2016 pm 01:04 PM
php

PHP即时输出结果到浏览器的方法:我们可以使用ob_flush()函数和flush()函数来强制浏览器刷新缓存,进而实现即时输出结果到浏览器中。

PHP怎么即时输出结果到浏览器

运行下面代码:

<?php
for ( $i = 0 ; $i < 10 ; $i ++ ) {
    echo $i ;
    sleep ( 1 ) ;
}
?>
Copy after login

类似上面的程序如果在PHP解释器中执行,每秒会输出一个数,和想象中一样。但是如果使用浏览器来访问,情况就有所不同。在浏览器中访问时,只有在十秒之后才会一次性地显示所有结果。

那么PHP怎么即时输出结果到浏览器?

可以使用ob_flush() 和flush() 来强制浏览器刷新缓存,程序改为:

<?php
for ( $i = 0 ; $i < 10 ; $i ++ ) {
    echo $i ;
    ob_flush ( ) ;
    flush ( ) ;
    sleep ( 1 ) ;
}
?>
Copy after login

再使用浏览器访问,四个浏览器中只有Firefox 即时输出了结果。这是因为不同的浏览器对缓冲的处理方式不同,Firefox在被要求强制刷新缓存时很听话,而IE需要在接收到256个字节后才会将内容即时展现在界面上,Safari 需要1024个字节,Opera 更有个性,只有在遇到HTML标签的时候才会即时输出(Safari也是如此)。

对于IE和Safari,可以在输出结果之前先输出大于限定数目的空白字符:

<?php
echo str_repeat ( " " , 1024 ) ;
for ( $i = 0 ; $i < 10 ; $i ++ ) {
    echo $i ;
    ob_flush ( ) ;
    flush ( ) ;
    sleep ( 1 ) ;
}
?>
Copy after login

而对于Opera、Safari遇到HTML标签后才会即时输出的问题,由于一般我们不会只往浏览器中输出纯文本内容,故可以不作考虑。对于上面的程序,可以在输出结果中加入HTML标签来达到目的:

<?php
echo str_repeat ( " " , 1024 ) ;
for ( $i = 0 ; $i < 10 ; $i ++ ) {
    echo $i . "<br>" ;
    ob_flush ( ) ;
    flush ( ) ;
    sleep ( 1 ) ;
}
?>
Copy after login

至此已基本实现了在各个浏览器中实现php执行结果实时输出并显示到浏览器的效果了,至于实际工作中,你可能是另外一种目的但是需要类似这种效果,则只需要根据需要做相应的修改即可。

除了上述方法外,PHP使用缓存即时输出内容(output buffering)也可行,不过经过测试还是上述的方法好用。

 
$buffer = ini_get(&#39;output_buffering&#39;);
echo str_repeat(&#39; &#39;,$buffer+1);     //防止浏览器缓存
ob_end_flush();     //关闭缓存
for( $i=1; $i<=10; $i++ ){
    echo &#39;第 &#39;.$i.&#39; 次输出.&#39;."<br />\n";
flush(); //刷新缓存(直接发送到浏览器)
    sleep(1);
}
echo &#39;输出完毕!&#39;;
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