PHP怎么即时输出结果到浏览器
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。
运行下面代码:
<?php for ( $i = 0 ; $i < 10 ; $i ++ ) { echo $i ; sleep ( 1 ) ; } ?>
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 ) ; } ?>
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 ) ; } ?>
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 ) ; } ?>
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。
$buffer = ini_get('output_buffering'); echo str_repeat(' ',$buffer+1); //防止浏览器缓存 ob_end_flush(); //关闭缓存 for( $i=1; $i<=10; $i++ ){ echo '第 '.$i.' 次输出.'."<br />\n"; flush(); //刷新缓存(直接发送到浏览器) sleep(1); } echo '输出完毕!';
更多相关知识,请访问 PHP中文网!!

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