原文地址：百度知道的php爬虫作者：好宏杰软件

<?php

class spider 
{ 
  private $content ; 
  private $contentlen ; 
  private $BestAnswer ; 
  private $CurPosition ;

function GetStart( $iStart
) 
  { 
    return
strpos( $this->content , '>' ,
$iStart )+1 ; 
  }

function GetContent ( $url
) 
  { 
   
$this->content =
file_get_contents($url); 
   
$this->contentlen = strlen(
$this->content ) ; 
    $start =
strpos( $this->content ,
'<title>') ; 
    $start =
$this->GetStart( $start ) ; 
    $end =
strpos( $this->content ,
'</title>' , $start )
; 
    $title =
substr( $this->content , $start ,
$this->$end-$start ) ; 
    if ( strpos(
$title , '_百度知道' , 1 ) < 1 ) 
   
{ 
     
return false; 
   
} 
    return ture
; 
  }

function GetTitle() 
  { 
    $start =
strpos( $this->content ,
'<title>') ; 
    if ( $start
> 0 ) 
   
{ 
     
$start = $this->GetStart( $start )
; 
     
$end = strpos( $this->content ,
'</title>' , $start )
; 
     
$this->CurPosition = $end ; 
     
return substr( $this->content , $start , $end-$start
) ; 
   
} 
    return NULL
; 
  }

function GetQTitle() 
  { 
    $start =
strpos( $this->content , 'span
class="question-title"' , $this->CurPosition )
; 
    if ( $start
> 0 ) 
   
{ 
     
$start = $this->GetStart( $start )
; 
     
$end = strpos( $this->content ,
'</span>' , $start )
; 
     
$this->CurPosition = $end ; 
     
return substr( $this->content , $start , $end-$start
) ; 
   
} 
    return NULL
; 
  }

function
GetClassFly() 
  { 
   
;

}

function
GetQContent() 
  { 
    
$start = strpos( $this->content , 'pre
id="question-content"' , $this->CurPosition )
; 
    
if ( $start > 0 ) 
    
{ 
      
$start = $this->GetStart( $start )
; 
      
$end = strpos( $this->content ,
'</pre>' , $start )
; 
      
$this->CurPosition = $end ; 
      
return substr( $this->content , $start , $end-$start
) ; 
    
} 
    
return NULL ; 
  }

function GetQsuply() 
  { 
    $start =
strpos( $this->content , 'id="question-suply"' ,
$this->CurPosition ) ; 
    if ( $start
> 0 ) 
   
{ 
     
$start = $this->GetStart( $start )
; 
     
$end = strpos( $this->content ,
'</pre>' , $start )
; 
     
$this->CurPosition = $end ; 
     
return substr( $this->content , $start , $end-$start
) ; 
   
} 
    return NULL
; 
  }

function GetAnswer() 
  { 
    $start =
strpos( $this->content , 'class="reply-text mb10"' ,
$this->CurPosition ) ; 
    if ( $start
> 0 ) 
   
{ 
     
$start = $this->GetStart( $start )
; 
     
$end = strpos( $this->content ,
'</pre>' , $start )
; 
     
$this->CurPosition = $end ; 
     
return substr( $this->content , $start , $end-$start
) ; 
   
} 
    return NULL
; 
  } 
}

ini_set('max_execution_time', '0'); 
$TestSpider = new spider() ; 
$Startqid = 1000001 ; 
$sndqid = 1000051 ; 
$standurl = 'http://zhidao.baidu.com/question/'
; 
$html = '.html' ; 
$url ; 
$NoUse = 0 ;

function microtime_float() 
{ 
  list($usec, $sec) = explode(" ",
microtime()); 
  return ((float)$usec +
(float)$sec); 
}

$time_start = microtime_float(); 
$answer ; 
for ($i = $Startqid ; $i < $sndqid ; $i++
) 
{ 
  $url = $standurl.$i.$html
; 
  if ( $TestSpider->GetContent (
$url ) ) 
  { 
    echo
'<br>正在爬取编号为'.$i.'的网页<br>'
; 
   
$TestSpider->GetTitle() ;
//得到网页标题,不用显示了 
    echo
'<font
color="green">问题：</font><font
color="red"><a target="_blank"
href="'.$url.'">
'.$TestSpider->GetQTitle().'</a></font><br>'
; //得到问题题目 
    echo
'<font
color="green">问题具体内容：</font>'.$TestSpider->GetQContent().'</font><br>'
; //得到问题内容，有可能不存在 
    echo
'<font
color="green">问题补充说明：</font>'.$TestSpider->GetQsuply().'</font><br>'
; //问题补充说明，有可能不存在 
    while (
($answer = $TestSpider->GetAnswer()) != NULL
)  
   
{ 
     
echo '<font
color="green">问题答案：</font>'.$answer.'</font><br>'
; //得到答案。有可能没有答案！ 
   
} 
    ob_flush()
; 
    flush()
; 
  } 
  else 
  { 
    echo
'<p>错误了<a
target="_blank" href="'.$url.'" style=
"color:#ff0000">'.$url.'</a></p>'
; 
    $NoUse++
; 
  } 
}

$time_end = microtime_float(); 
$time = $time_end - $time_start; 
$i = $i-$Startqid ; 
echo
'<p>爬取'.$i.'个网页用时'.$time.'秒</p>其中跳过'.$NoUse.'个无效网页！'
;

?>