PHP cURL

cURL – Client URL library is used to communicate with different type of servers with protocols FTP, HTTP, telnet, gopher and more. In PHP, we have to install libcurl library for using cURL function. If we used any one of AMP bundle like XAMPP, to create PHP environment, then the cURL library will come up with this bundle.

After cURL installation, we should enable this extension in PHP configuration file.

//Remove semi colon (;) to enable
;extension=php_curl.dll

cURL Supported Operations

For handling remote file access, the cURL as an intermediary is used for,

  • Form submitting
  • Authentication
  • File upload
  • File transfer

Without cURL, we can use PHP file system functionsallow_url_fopen configuration directive which is not preferable because of security reasons. For example, file_get_contents() returns remote data including some untrusted internet content.

PHP cURL Delimiters

In a PHP program the cURL portion should be enclosed within these two pair of functions.

$ch = curl_init(URL Syntax);
...
curl_close($ch);

The curl_init() function returns cURL session handle with respect to the given file URL. And then, curl_close() function will be an end delimiter to close cURL session with respect to its handle.

cURL Options

PHP curl_setopt() function is used to set options. It receives cURL handle, option’s name and value as its parameters.

We can use another cURL function curl_setopt_array() to set array of multiple options at a push.

curl_setopt ($ch, CURLOPT_HEADER, 1);

cURL Option Constants

  • CURLOPT_FILE – target file to write cURL result.
  • CURLOPT_URL – URL from where we need to get data. If this URL is specified with curl_init(), then no need to set this option
  • CURLOPT_RETURNTRANSFER – to return result in string format into a variable instead of printing it to the browser.
  • CURLOPT_HTTPHEADER – to set header fields as an array.
  • CURLOPT_POST – set to TRUE to perform HTTP POST.
  • CURLOPT_USERPWD – to set username/password if required to connect remote server.

php_curl

PHP cURL Request

Like PHP, the GET and POST methods are used for seding cURL request where GET is default. The CURLOPT_POST constant is used for sending POST request. And the parameters CURLOPT_POSTFIELDS is for sending parameter array of the field:value pairs.

cURL Execution

After setting request methods and parameters, curl_exec() function is used for executing cURL request.

$result = curl_exec($ch);

This function returns either boolean values or string data based on the value of option CURLOPT_RETURNTRANSFER.

PHP cURL Example

This PHP example is to get the body content from the given remote URL.

<?php
$url = "http://php.net/";
$content = curlRequest($url);
print $content;

function curlRequest($url) {
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $url);
$response = curl_exec($ch);
$body = substr( $response, $header_size );
fclose($ch);
return $content;
}
?>

This PHP code tutorial was published on October 18, 2013.

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