Xpath中preg_match的错误是什么?未定义的偏移量:1 - What is the error of preg_match in Xpath? Undefined offset: 1

What is the error of preg_match in Xpath? Undefined offset: 1

我试图从属性id中获取id，代码如下：

<?php
$getURL = file_get_contents('http://realestate.com.kh/residential-for-rent-in-phnom-penh-daun-penh-phsar-chas-2-beds-apartment-1001192296/');
$dom = new DOMDocument();
@$dom->loadHTML($getURL);
$xpath = new DOMXPath($dom);
/*echo $xpath->evaluate("normalize-space(substring-before(substring-after(//p[contains(text(),'Property ID:')][1], 'Property ID:'), '–'))");*/
$id = $xpath->evaluate('//div[contains(@class,"property-table")]')->item(0)->nodeValue;
preg_match("/Property ID :(.*)/", $id, $matches);
echo $matches[1];

但它不起作用；

Notice: Undefined offset: 1 in W:'Xampp'htdocs'X'index.php on line 12

怎么了？如果我制造像这样的刺痛

$id ="Property Details Property Type : Apartment Price $ 350 pm Building Size 72 Sqms Property ID : 1001192296";

并在我的代码中替换它。那么，myselt创建的数据和xpath中的grab创建的数据之间有什么区别呢？提前感谢您对我的帮助。

您的preg_match()不工作，因为您从xpath获得的nodeValue正是这样的：

Property Details
                            Property Type : 
                         Apartment 

                    Price
                    $ 350 pm

                Building Size
                72 Sqms

                Property ID 
                 : 
                1001192296

所以你必须这样尝试：

$getURL = file_get_contents('http://realestate.com.kh/residential-for-rent-in-phnom-penh-daun-penh-phsar-chas-2-beds-apartment-1001192296/');
$dom = new DOMDocument();
@$dom->loadHTML($getURL);
$xpath = new DOMXPath($dom);
/*echo $xpath->evaluate("normalize-space(substring-before(substring-after(//p[contains(text(),'Property ID:')][1], 'Property ID:'), '–'))");*/
$id = $xpath->evaluate('//div[contains(@class,"property-table")]')->item(0)->nodeValue;
$id = preg_replace('!'s+!', ' ', $id);
preg_match("/Property ID :(.*)/", $id, $matches);
echo $matches[1];

这（$id = preg_replace('!'s+!', ' ', $id);）将把所有标签、单词之间的空白合并为一个空白。

更新：由于下面的注释，我现在获得了带有$xpath->evaluate()的HTML的全文，并尝试匹配所有属性ID（比如只有数字和P数字）。

$getURL = file_get_contents('http://realestate.com.kh/residential-for-rent-in-phnom-penh-daun-penh-phsar-chas-2-beds-apartment-1001192296/');
$dom = new DOMDocument();
@$dom->loadHTML($getURL);
$xpath = new DOMXPath($dom);
// this only returns the text of the whole page without html tags
$id = $xpath->evaluate( "//html" )->item(0)->nodeValue;
$id = preg_replace('!'s+!', ' ', $id);
// not a good regex, but matches the property IDs
preg_match_all("/Property ID( |):[ |](('w{0,1}[-]|)'d*)/", $id, $matches);
// after the changes you have to go for the matches is $matches[2]
foreach( $matches[2] as $property_id ) {
    echo $property_id."<br>";
}

您需要检查preg_match()是否真的找到了任何东西。

如果没有结果，就不会有$matches[1]。您应该使用if(count($matches)>1) {... }来解决您遇到的问题。