Getting Started with PHP: CURL Extension

PHP is a language widely used in web development, and CURL is one of the most widely used extensions in PHP. This article will introduce you to the basic usage and application of CURL to help beginners get started quickly.

1. Introduction to CURL

CURL is a command line tool that uses URL syntax to transmit data. It is also a library that supports multiple protocols and can run on multiple platforms. When using the CURL extension in PHP, it is mainly used for network communication through protocols such as HTTP and HTTPS to send data to other servers, obtain server responses, simulate form submission, etc.

2. CURL installation

To use the CURL extension in PHP, you need to confirm that the local environment has support for the CURL library. In Linux and Mac OS

After the installation is completed, you can check whether the installation has been completed through the

phpinfo()

function. If it prompts that curl support is enabled, it means that the CURL extension is ready. 3. Basic usage of CURL

Send GET request

1. The basic format of sending GET request is:

sudo apt-get install libcurl4-openssl-dev // Debian/Ubuntu 

sudo yum install curl-devel // CentOS/Fedora

Among them,

curl_init()

The function is used to initialize a CURL object, the curl_setopt() function is used to set the options of the CURL request, the curl_exec() function is used to execute the CURL request And get the response result, curl_close() function is used to close the CURL object. In the above example, we use the

curl_setopt()

function to set the requested URL, CURLOPT_RETURNTRANSFER option and CURLOPT_HEADER option. Among them, when the CURLOPT_RETURNTRANSFER option is set to 1, it means that the obtained response result will be returned in the form of a string. CURLOPT_HEADERWhen the option is set to 0, it means that the response header information is not included in the response result.

Send POST request

The basic format of sending POST request is:

<?php
//创建CURL对象
$ch = curl_init();
//设置URL和相应的选项
curl_setopt($ch, CURLOPT_URL, "http://api.example.com/user?id=123");
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch, CURLOPT_HEADER, 0);
//执行CURL请求并获取响应结果
$output = curl_exec($ch);
//关闭CURL对象
curl_close($ch);
//输出响应结果
echo $output; 
?>

Among them,

curl_setopt()

function is newly added Two options are available: CURLOPT_POST and CURLOPT_POSTFIELDS. When the CURLOPT_POST option is set to 1, it means that the request is sent in POST mode. When the CURLOPT_POSTFIELDS option is set to a string, it means that these data are sent as the body of the POST request. It should be noted that in order to correctly send POST data to the server, the correct

Content-Type

header information needs to be set. This can be set via the CURLOPT_HTTPHEADER option of the curl_setopt() function. 4. Advanced usage of CURL

Set HTTP header information

You can use the

curl_setopt()

functionCURLOPT_HTTPHEADER option to set HTTP header information. <div class="code" style="position:relative; padding:0px; margin:0px;"><pre class='brush:php;toolbar:false;'>&lt;?php //创建CURL对象 $ch = curl_init(); //设置URL和相应的选项 curl_setopt($ch, CURLOPT_URL, &quot;http://api.example.com/user&quot;); curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1); curl_setopt($ch, CURLOPT_HEADER, 0); curl_setopt($ch, CURLOPT_POST, 1); curl_setopt($ch, CURLOPT_POSTFIELDS, &quot;id=123&amp;name=John&quot;); //执行CURL请求并获取响应结果 $output = curl_exec($ch); //关闭CURL对象 curl_close($ch); //输出响应结果 echo $output; ?&gt;</pre><div class="contentsignin">Copy after login</div></div>The above code sets the Content-Type header information to application/json, sets a header information named Authorization, and sets a value for it. The purpose of this header information is to provide a security token for the request so that the server can verify the legitimacy of the request.

SSL/TLS Verification

SSL/TLS verification is a mechanism that ensures the security of the request by judging the legitimacy of the encryption certificate. CURL provides a variety of security verification methods, which can be achieved through the

CURLOPT_SSL_VERIFYPEER

and CURLOPT_SSL_VERIFYHOST options of the curl_setopt() function. For example, the following code can be used to turn off the verification of the SSL certificate:

curl_setopt($ch, CURLOPT_HTTPHEADER, array('Content-Type: application/json', 'Authorization: Bearer xxx'));

It should be noted that in actual applications, enabling the verification of the SSL certificate as much as possible is to ensure the security of the request. Very important.

Cookie processing

CURL can automatically handle HTTP Cookies, which provides great convenience for managing user sessions. We can use the CURLOPT_COOKIEJAR option of the curl_setopt() function to save the cookie information returned by the server.

curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, false);

When sending the next request, use the CURLOPT_COOKIEFILE option of the curl_setopt() function to specify the file path where the cookie information is saved.

curl_setopt($ch, CURLOPT_COOKIEJAR, '/tmp/cookies');

4. Summary

Through the introduction of this article, I believe that readers have initially understood the basic usage of CURL extension, including sending GET/POST requests, setting HTTP header information, SSL/ TLS verification and cookie handling, these contents will help us better program network communication. Next, you can try to use CURL extensions to develop some practical network applications, continue to learn more, and improve your programming skills.

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