Problems and solutions encountered by PHP when using Curl in Linux environment

In the Linux development environment, PHP uses Curl as a general HTTP client tool, which can be used for communication between web servers and for obtaining third-party API interface data. However, we may encounter some problems while using Curl. In this article, I'll cover some common Curl problems and how to solve them.

1. Environment installation
Before using Curl, you need to ensure that the Curl extension has been installed in the Linux environment. The specific installation process is as follows:

1. Enter the download directory of the PHP source code in the terminal and download the required version of the PHP source code.

2. Unzip and enter the source directory, and then execute the following command to compile and install.

./configure --with-curl=/usr/local/curl
--enable-mbstring
--with-zlib
--with-mcrypt
-- with-openssl
--enable-fpm
--with-fpm-user=www
--with-fpm-group=www
--prefix=/usr/local/php
--with-config-file-path=/usr/local/php/etc
--enable-opcache
--enable-debug
--with-mysqli
--enable- pcntl
--enable-sockets

make && make install

3. After the installation is complete, you can add the following code to the php.ini configuration file to enable the Curl extension.

extension=curl.so

4. Restart apache or php-fpm service, and execute php -m to check whether the Curl extension is enabled.

2. SSL Certificate Authentication Issues
When using Curl, if the other party's API interface uses the HTTPS protocol, we need to configure the default root certificate locally. For Guzzle and Symfony Http Client, follow the steps below to achieve this:

1. Download the CA certificate

$ curl -o cacert.pem https://curl.haxx.se/ca/cacert .pem

or

$ wget https://curl.haxx.se/ca/cacert.pem -O cacert.pem

2. Set the environment variable CURL_CA_BUNDLE

export CURL_CA_BUNDLE=/path/to/cacert.pem

3. Proxy setting problem
When we use Curl to obtain third-party API interface data in a Linux environment, sometimes we need to set a proxy . The following is how to use Curl to set up a proxy:

1. Example of using the proxy server IP as 192.168.100.10 and the port number as 8080

curl_setopt($curl, CURLOPT_PROXY, '192.168.100.10: 8080');

2. If the proxy server requires authentication, you also need to set the proxy username and password.

curl_setopt($curl, CURLOPT_PROXYUSERPWD, 'username:password');

4. Request header setting issues
When using Curl to send a request, some request header information needs to be and sent to the API interface. Here is an example of how to set the request headers:

$curl = curl_init($url);

$headers = array(

           'Content-Type:application/json',
           'Authorization:Bearer ' . $accessToken,
       );

curl_setopt($curl, CURLOPT_HTTPHEADER, $ headers);

5. File upload issues
In the API interface, sometimes we need to upload files. In this case, we can use Curl's CURLOPT_POSTFIELDS parameter to upload files. The following is an example of uploading files:

$data = array(
"myfile" => curl_file_create(

   '/path/to/myfile.jpg',
   'image/jpeg',
   'myfile.jpg'

),
);

curl_setopt($curl, CURLOPT_POSTFIELDS, $data );

6. Problems with parsing return data
When we use Curl to obtain third-party API interface data, we need to parse the return results. The following is an example of parsing JSON response data:

$response = curl_exec($curl);
if (curl_errno($curl)) {

$error_msg = curl_error($curl);
return $error_msg;

}
$response = json_decode($response, true);

The above is an introduction to the problems and solutions encountered when using Curl in the Linux development environment. I hope it can be helpful to everyone.

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