Detailed explanation of several methods of php crawling pages

This article is a detailed analysis and introduction to several methods of crawling pages with PHP. Friends who need it can refer to it

I am doing some weather forecastor RSS subscription programs When doing this, it is often necessary to capture non-local files. Generally, PHP is used to simulate browser access, and the URL address is accessed through HTTP requests, and then the HTML source code or XML data is obtained. We cannot output the data directly, and often need to modify the content. Extract it and then format it to display it in a more user-friendly way.
Let’s briefly talk about several methods and principles of PHP crawling pages:
1. The main methods of PHP crawling pages:
1. file( ) function
2. file_get_contents() function
3. fopen()->fread()->fclose() mode
4.curl mode
5. fsockopen() function socket mode
6. Use plug-ins (such as: http://sourceforge.net/projects/snoopy/)

2. PHP mainly parses html or xml code Method:
1. file() function

The code is as follows:

<?php 
$url=&#39;http://t.qq.com&#39;; 
$lines_array=file($url); 
$lines_string=implode(&#39;&#39;,$lines_array); 
echo htmlspecialchars($lines_string);

2. file_get_contents() function
Using file_get_contents and fopen must enable allow_url_fopen. Method: Edit php.ini and set allow_url_fopen = On. When allow_url_fopen is turned off, neither fopen nor file_get_contents can open remote files.

The code is as follows:

<?php 
$url=&#39;http://t.qq.com&#39;; 
$lines_string=file_get_contents($url); 
echo htmlspecialchars($lines_string);

3. fopen()->fread()->fclose() mode

The code is as follows:

<?php 
$url=&#39;http://t.qq.com&#39;; 
$handle=fopen($url,"rb"); 
$lines_string=""; 
do{ 
    $data=fread($handle,1024);
     if(strlen($data)==0) {
        break;
    } 
    $lines_string.=$data; 
}while(true); 
fclose($handle); 
echo htmlspecialchars($lines_string);

4. curl method
Using curl requires space to enable curl. Method: Modify php.ini under Windows, remove the semicolon in front of extension=php_curl.dll, and copy ssleay32.dll and libeay32.dll to C:\WINDOWS\system32; under Linux, install the curl extension.

The code is as follows:

<?php 
$url=&#39;http://t.qq.com&#39;; 
$ch=curl_init(); 
$timeout=5; 
curl_setopt($ch, CURLOPT_URL, $url); 
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1); 
curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, $timeout); 
$lines_string=curl_exec($ch); 
curl_close($ch); 
echo htmlspecialchars($lines_string);

5. fsockopen() function socket mode
Whether the socket mode can be executed correctly is also related to the server settings. , you can check which communication protocols are enabled by the server through phpinfo. For example, my local php socket does not enable http, so I can only use udp to test it.

The code is as follows:

<?php                                                                                                                                                
$fp = fsockopen("udp://127.0.0.1", 13, $errno, $errstr)；
if (!$fp) { 
    echo "ERROR: $errno - $errstr<br />\n"
} else { 
    fwrite($fp, "\n")
    echo fread($fp, 26)
    fclose($fp)
}

6. Plug-ins
There should be more plug-ins on the Internet. The snoopy plug-in was found online. If you are interested You can research it.

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