How PHP uses the xmllint command to process xml and html, xmllintxml

How PHP uses the xmllint command to process xml and html, xmllintxml_PHP tutorial

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Release： 2016-07-13 10:11:35

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PHP uses the xmllint command to process xml and html, xmllintxml

The example in this article describes how PHP uses the xmllint command to process xml and html. Share it with everyone for your reference. The specific analysis is as follows:

xmllint is a very convenient tool for processing and verifying xml and processing html. Under Linux, you can use this command as long as libxml2 is installed. First, let’s take a look at an example of processing HTML using the --html and --xpath parameters:

An example is as follows:

Copy code The code is as follows:

curl http://www.bkjia.com /ip/?q=8.8.8.8 2>/dev/ null |

In the above example, only the content of the text part is obtained by extracting the result (ul#csstb) after querying the ownership of the IP address on 123cha. The result after executing the above script statement is as follows:

[Your query]:8.8.8.8
Main data of this site:
USA> Auxiliary data of this site: Google Public DNS provided:hypo
United States Google’s free Google Public DNS provides: zwstar reference data 1: United States
Reference data two: United States

Let’s take a look at the usage of other main parameters with examples.

1. --format
This parameter is used to format the xml so that it has good readability. Suppose there is xml (person.xml) with the following content:

Copy code The code is as follows:

ball30 male

After performing the following operations, the output will be in a more readable xml format:

Copy code The code is as follows:

#xmllint --format person.xml

ball
30
male

2. --noblanks
Contrary to --format, sometimes in order to save transmission volume, we want to remove the blanks in xml. In this case, we can use the --noblanks command. Assume that the content of xml (person.xml) is as follows

Copy code The code is as follows:

ball
30
male

After executing this parameter operation, the output result is:

Copy code The code is as follows:

#xmllint --noblanks person.xml

ball
3. --schema

Use scheam to verify the correctness of xml files (XML Schema is an XML-based DTD replacement) Assume that there are xml files (person.xml) and scheam files (person.xsd). The contents are as follows
person.xml

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The code is as follows:

ball

30
male

person.xsd

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The code is as follows:

按如下命令执行后的结果是：

复制代码代码如下:

#xmllint --schema person.xsd person.xml


      ball
      30
      male

person.xml validates
注：默认情况下，验证后会输出验证的文件内容，可以使用 --noout选项去掉此输出，这样我们可以只得到最后的验证结果。

复制代码代码如下:

#xmllint --noout --schema person.xsd person.xml

person.xml validates
下面我们改动person.xml，使这份文件age字段和sex都是不符合xsd定义的。

复制代码代码如下:

#xmllint --noout --schema person.xsd person.xml
person.xml:4: element age: Schemas validity error : Element 'age': 'not age' is not a valid value of the atomic type 'xs:integer'.
person.xml:5: element sex: Schemas validity error : Element 'sex': [facet 'enumeration'] The value 'test' is not an element of the set {'male', 'female'}.
person.xml:5: element sex: Schemas validity error : Element 'sex': 'test' is not a valid value of the local atomic type.
person.xml fails to validate

可以看到xmllint成功的报出了错误！

4、关于--schema的输出

在讲输出之前先看下面一个场景，假如你想通过php执行xmllint然后拿到返回结果，你的代码通常应该是这个样子valid.php

复制代码代码如下:

$command = "xmllint --noout --schema person.xsd person.xml";
exec($command, $output, $retval);
//出错时返回值不为0
if ($retval != 0){
var_dump($output);
}
else{
echo "yeah!";
}

We keep the errors in person.xml above.

Execute this code and you will find that the output you get is not an error, but array(0) {}, amazing!
Why is this happening?

Because of xmllint --schema, if an error occurs during verification, the error message will not be displayed through the standard output (stdout), but through the standard error (stderr).

The output parameter of exec can only get the content displayed by the standard output (stdout).
Therefore, in order to get the error message, we need to redirect standard error to standard output and modify the code accordingly:

Copy code The code is as follows:

$command = "xmllint --noout --schema person.xsd person.xml 2>$1";

Execute valid.php again and get the error message successfully!

Examples are as follows:
First create an xml document, named po.xml, with the following content:

Copy code The code is as follows:

123 Maple Street

Hurry, my lawn is going wild!


                                                                                                                                                                                                                  Lawnmower
                                             1
                                                                                                                                                                                                      148.95


                                     Baby Monitor
                                             1
                                                                                                                                                                                                               39.98
                1999-05-21


Then the schema file written for po.xml is named po.xsd and the content is as follows:

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The code is as follows: