我修改了一些我在这里找到的爬虫，一切都运行正常，但我遇到了一些问题。第一个是致命错误：在null上调用成员函数hasAttribute（）。我怎么能绕过这个？第一条记录总是生成空的，我也不知道为什么。 另一件事是我的XML会在每条记录之后覆盖而不是添加更多元素。
非常感谢您的帮助！
<?php
ini_set('display_errors', 1);
ini_set('display_startup_errors', 1);
error_reporting(E_ALL);
/*
* howCode Web Crawler Tutorial Series Source Code
* Copyright (C) 2016
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* https://howcode.org
*
*/
// This is our starting point. Change this to whatever URL you want.
$start = "https://www.xxxxx.com/xxx.xml";
// Our 2 global arrays containing our links to be crawled.
$already_crawled = array();
$crawling = array();
function array_to_xml( $data, &$xml_data ) {
foreach( $data as $key => $value ) {
if( is_numeric($key) ){
$key = 'item'.$key; //dealing with <0/>..<n/> issues
}
if( is_array($value) ) {
$subnode = $xml_data->addChild($key);
array_to_xml($value, $subnode);
} else {
$xml_data->addChild("$key",htmlspecialchars("$value"));
}
}
}
function get_details($url) {
// The array that we pass to stream_context_create() to modify our User Agent.
$options = array('http'=>array('method'=>"GET", 'headers'=>"User-Agent: howBot/0.1\n"));
// Create the stream context.
$context = stream_context_create($options);
// Create a new instance of PHP's DOMDocument class.
$doc = new DOMDocument();
//var_dump($doc);
// Use file_get_contents() to download the page, pass the output of file_get_contents()
// to PHP's DOMDocument class.
@$doc->loadHTML(@file_get_contents($url, false, $context));
// Create an array of all of the title tags.
$title = $doc->getElementsByTagName("h1");
// There should only be one <title> on each page, so our array should have only 1 element.
$title = $title->item(0)->nodeValue;
$data->title = $title;
// Give $description and $keywords no value initially. We do this to prevent errors.
$description = "";
$keywords = "";
// Create an array of all of the pages <meta> tags. There will probably be lots of these.
$proddesc="product-description";
$finder = new DomXPath($doc);
$spaners = $finder->query("//*[contains(@class, '$proddesc')]");
$spaners = $spaners->item(0)->nodeValue;
$data->spanner = $spaners;
$imgdata = "product-big-picture";
$finder8 = new DomXPath($doc);
$img = $finder8->query('//*[@class="product-big-picture"]');
if ($img->item(0)->hasAttribute('src')){
$img = $img->item(0)->getAttribute('src');
}else{
$img='';
}
$data->img = $img;
var_dump($img);
$proddescother ="other-desc";
$finder2 = new DomXPath($doc);
$descOther = $finder2->query("//*[contains(@class, '$proddescother')]");
$descOther = $descOther->item(0)->nodeValue;
$data->desc = $descOther;
$eanhtml = "product-info";
$finder3 = new DomXPath($doc);
$ean = $finder3->query("//*[contains(@class, '$eanhtml')]");
$ean = $ean->item(0)->nodeValue;
//$ShortDesc = $doc->getElementsByClassName("product-description");
//var_dump($spaner);
//$LongDesc = $doc->getElementsByClassName("other-desc");
//$ean = $doc->getElementsByClassName("product-info");
// Loop through all of the <meta> tags we find.
/*for ($i = 0; $i < $metas->length; $i++) {
$meta = $metas->item($i);
// Get the description and the keywords.
if (strtolower($meta->getAttribute("name")) == "description")
$description = $meta->getAttribute("content");
if (strtolower($meta->getAttribute("name")) == "keywords")
$keywords = $meta->getAttribute("content");
}*/
// Return our JSON string containing the title, description, keywords and URL.
$eanfinalPiece = explode(':', $ean);
$eanfinal = $eanfinalPiece[1];
$data->ean = $eanfinal;
$product_data = json_encode($data);
var_dump($product_data);
//$json = '{ "Title": "'.str_replace("\n", "", $title).'", "Short Desc": "'.str_replace("\n", "", $spaners).'", "Long Desc": "'.str_replace("\n", "", $descOther).'", "EAN": "'.$eanfinal.'"},';
$array = json_decode($product_data, true);
//var_dump($json);
$xml_data = new SimpleXMLElement('<?xml version="1.0"?><data></data>');
array_to_xml($data,$xml_data);
//saving generated xml file;
$result .= $xml_data->asXML('data.xml');
return true;
}
function follow_links($url) {
// Give our function access to our crawl arrays.
global $already_crawled;
//var_dump($already_crawled);
global $crawling;
// The array that we pass to stream_context_create() to modify our User Agent.
$options = array('http'=>array('method'=>"GET", 'headers'=>"User-Agent: howBot/0.1\n"));
// Create the stream context.
$context = stream_context_create($options);
// Create a new instance of PHP's DOMDocument class.
$doc = new DOMDocument();
// Use file_get_contents() to download the page, pass the output of file_get_contents()
// to PHP's DOMDocument class.
@$doc->loadHTML(@file_get_contents($url, false, $context));
// Create an array of all of the links we find on the page.
$linklist = $doc->getElementsByTagName("loc");
//var_dump($linklist);
// Loop through all of the links we find.
foreach ($linklist as $link) {
$l = $link->textContent;
//var_dump($link->textContent);
// Process all of the links we find. This is covered in part 2 and part 3 of the video series.
if (substr($l, 0, 1) == "/" && substr($l, 0, 2) != "//") {
$l = parse_url($url)["scheme"]."://".parse_url($url)["host"].$l;
} else if (substr($l, 0, 2) == "//") {
$l = parse_url($url)["scheme"].":".$l;
} else if (substr($l, 0, 2) == "./") {
$l = parse_url($url)["scheme"]."://".parse_url($url)["host"].dirname(parse_url($url)["path"]).substr($l, 1);
} else if (substr($l, 0, 1) == "#") {
$l = parse_url($url)["scheme"]."://".parse_url($url)["host"].parse_url($url)["path"].$l;
} else if (substr($l, 0, 3) == "../") {
$l = parse_url($url)["scheme"]."://".parse_url($url)["host"]."/".$l;
} else if (substr($l, 0, 11) == "javascript:") {
continue;
} else if (substr($l, 0, 5) != "https" && substr($l, 0, 4) != "http") {
$l = parse_url($url)["scheme"]."://".parse_url($url)["host"]."/".$l;
}
// If the link isn't already in our crawl array add it, otherwise ignore it.
if (!in_array($l, $already_crawled)) {
$already_crawled[] = $l;
$crawling[] = $l;
// Output the page title, descriptions, keywords and URL. This output is
// piped off to an external file using the command line.
echo get_details($l)."\n";
}
}
// Remove an item from the array after we have crawled it.
// This prevents infinitely crawling the same page.
array_shift($crawling);
// Follow each link in the crawling array.
foreach ($crawling as $site) {
follow_links($site);
}
}
// Begin the crawling process by crawling the starting link first.
follow_links($start);
答案 0 :(得分：0)
尝试替换
if ($img->item(0)->hasAttribute('src')){
与
if ($img->item(0) && $img->item(0)->hasAttribute('src')){