What is the usage of curl under php?

The usage of curl under PHP is: 1. Use CURL to send a request; 2. Get the output information of the CURL request; 3. Use CURL to send a GET request; 4. Use CURL to send a POST request.

The usage of curl under php is:

1. The basic process of sending requests using CURL

Using CURL's PHP extension to complete sending an HTTP request generally involves the following steps:

1. Initialize the connection handle;

2. Set CURL options;

3. Execute and obtain the results;

4. Release the VURL connection handle.

The following program fragment is a typical process of using CURL to send HTTP

// 1. 初始化
$ch = curl_init();
// 2. 设置选项，包括URL
curl_setopt($ch,CURLOPT_URL,"http://www.codetc.com");
curl_setopt($ch,CURLOPT_RETURNTRANSFER,1);
curl_setopt($ch,CURLOPT_HEADER,0);
// 3. 执行并获取HTML文档内容
$output = curl_exec($ch);
if($output === FALSE ){
 echo "CURL Error:".curl_error($ch);
}
// 4. 释放curl句柄
curl_close($ch);

Four functions are used in the above code

curl_init()andcurl_close()It is to initialize the CURL connection and close the CURL connection respectively, which are relatively simple.

curl_exec()Execute a CURL request. If no error occurs, the function returns the data returned by the corresponding URL, expressing satisfaction as a string; if an error occurs, the function returns FALSE. It should be noted that the equal sign is used to determine whether the output is FALSE. This is to distinguish between returning an empty string and an error.

The most important function in the CURL function library is curl_setopt(), which can customize HTTP requests by setting the options defined by the CURL function library. Three important options are used in the above code snippet:

• CURLOPT_URL specifies the requested URL;

• CURLOPT_RETURNTRANSFER is set to 1 to execute later The return of the curl_exec function is the return string of the URL, instead of directing the return string to the standard output and returning TRUE;

• CURLLOPT_HEADER is set to 0 to indicate that no HTTP header information is returned.

There are many options for CURL, you can check it out on PHP’s official website (http://www.php.net/manual/en/function.curl-setopt.php) List of all options supported by CURL.

2. Obtain the output information of the CURL request

After the curl_exec() function is executed, you can use the curl_getinfo() function to obtain the CURL request output Related information, the sample code is as follows:

curl_exec($ch);
$info = curl_getinfo($sh);
echo ' 获取 '.$info['url'].'耗时'.$info['total_time'].'秒';

In the above code, curl_getinfo returns an associative array, containing the following data:

• url: network address.

• content_type: Content encoding.

• http_code: HTTP status code.

• header_size: The size of the header.

• request_size: The size of the request.

• filetime: The time when the file was created.

• ssl_verify_result: SSL verification result.

• redirect_count: Jump count.

• total_time: Total time taken.

• namelookup_time: DNS query takes time.

• connect_time: Time spent waiting for connection.

• pretransfer_time: Pretransfer preparation time.

• size_uplpad: The size of the uploaded data.

• size_download: The size of the downloaded data.

• speed_download: Download speed.

• speed_upload: Upload speed.

• download_content_length: The length of the download content.

• upload_content_length: The length of the uploaded content.

• starttransfer_time: Timetable to start transfer.

• redirect_time: redirection takes time.

curl_getinfo()The function also has an optional parameter $opt, through which you can set some constants, corresponding to the field above. If the first Two parameters, then only the specified information is returned. For example, if $opt is set to CURLINFO_TOTAL_TIME, then the curl_getinfo() function will only return total_time, which is the time consumed by the total transmission. When you only need to pay attention to certain transmission information, it is very convenient to set the $opt parameter. Significant.

3. Use CURL to send a GET request

How to use CURL to send a GET request. The key to sending a GET request is to assemble a URL in the correct format. The request address and GET data are separated by a "?", then the name and value of the GET variable are separated by "=", and each GET name and value are connected by "&". PHP provides us with a function specifically used to assemble the GET request and data parts - http_build_query. This function accepts an associative array and returns the GET request string described by the associated data. Using this function, combined with the general process of CURL sending HTTP requests, we closed a function that sends GET requests - doCurlGetRequest. The specific code is as follows:

/**
 *@desc 封闭curl的调用接口，get的请求方式。
*/
function doCurlGetRequest($url,$data,$timeout = 5){
 if($curl == "" || $timeout <= 0){
 return false;
 }
 $url = $url.&#39;?&#39;.http_bulid_query($data);
 $con = curl_init((string)$url);
 curl_setopt($con, CURLOPT_HEADER, false);
 curl_setopt($con, CURLOPT_RETURNTRANSFER,true);
 curl_setopt($con, CURLOPT_TIMEOUT, (int)$timeout);
 return curl_exec($con);
}

4. Use CURL to send POST requests

You can use the option CURLOPT_POSTFIELDS provided by CURL. Set this option to POST string data to put the request in the body. Similarly, we implemented a function to send a POST request - doCurlPostRequest, the code is as follows:

/**
** @desc 封装 curl 的调用接口，post的请求方式
**/
function doCurlPostRequest($url,$requestString,$timeout = 5){
 if($url == &#39;&#39; || $requestString == &#39;&#39; || $timeout <=0){
 return false;
 }
 $con = curl_init((string)$url);
 curl_setopt($con, CURLOPT_HEADER, false);
 curl_setopt($con, CURLOPT_POSTFIELDS, $requestString);
 curl_setopt($con, CURLOPT_POST,true);
 curl_setopt($con, CURLOPT_RETURNTRANSFER,true);
 curl_setopt($con, CURLOPT_TIMEOUT,(int)$timeout);
 return curl_exec($con); 
}

In addition to setting CURLOPT_POSTFIELDS in the above code, we also set CURL_POST to true, identifies this request as a POST request. GET data can also be transmitted in POST requests. You only need to assemble the GET request data in the URL.

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