[php] Fatal error: Call to undefined function curl_init()

<?php
$filename = "xx.gif";
$handle = fopen($filename, "r");
$data = fread($handle, filesize($filename));

// $data is file data
$pvars   = array('image' => base64_encode($data), 'key' => IMGUR_API_KEY);
$timeout = 30;
$curl    = curl_init();

curl_setopt($curl, CURLOPT_URL, 'http://api.imgur.com/2/upload.xml');
curl_setopt($curl, CURLOPT_TIMEOUT, $timeout);
curl_setopt($curl, CURLOPT_POST, 1);
curl_setopt($curl, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($curl, CURLOPT_POSTFIELDS, $pvars);

$xml = curl_exec($curl);

curl_close ($curl);

var_dump($xml);
?>

I'm playing with the Imgur API, but it doesn't seems to work. PHP.net says that curl_init() is in PHP5, but my host says it isn't. How can I make this work?

do this

sudo apt-get install php-curl

and restart server

sudo service apache2 restart

This is from the official website. php.net

After installation of PHP.

Windows

Move to Windows\system32 folder: libssh2.dll, php_curl.dll, ssleay32.dll, libeay32.dll

Linux

Move to Apache24\bin folder libssh2.dll

Then uncomment extension=php_curl.dll in php.ini

There is solution with all necessary details for Windows 7 x64:

http://www.youtube.com/watch?v=7qNTi1sEfE8

It is in French, but you can understand everything! I solved same problem, even don't speak French. :-)

Many answers forget to mention that you need to add new version of php_curl.dll file from this location: http://www.anindya.com/php-5-4-3-and-php-5-3-13-x64-64-bit-for-windows/

I added new version of php_curl.dll from archive php_curl-5.4.3-VC9-x64.zip to folders: C:\wamp\bin\php\php5.4.3\ext and C:\Windows\System32 and everything was fine!

For Ubuntu

Install Curl extension for PHP & restart apache server.

sudo apt-get install php5-curl
sudo service apache2 restart

For Windows

Problem arises because of not including the lib_curl.dll to PHP. also load following extension if not working,so those extension in php.ini or remove comment if already exist in php.ini file then remove comment.

extension=php_bz2.dll
extension=php_curl.dll
extension=php_dba.dll

Now restart apache server. If you get an error "Unable to Load php_curl.dll", copy SSLEAY32.PHP, libEAY32.dll (OpenSSL) Libraries to the System32 folder.

for php 7.0 on ubuntu use

sudo apt-get install php7.0-curl

And finally,

sudo service apache2 restart 

or

sudo service nginx restart

Don't have enough reputation to comment yet. Using Ubuntu and a simple:

sudo apt-get install php5-curl
sudo /etc/init.d/apache2 restart

Did NOT work for me.

For some reason curl.so was installed in a location not picked up by default. I checked the extension_dir in my php.ini and copied over the curl.so to my extension_dir

cp /usr/lib/php5/20090626/curl.so  /usr/local/lib/php/extensions/no-debug-non-zts-20090626

Hope this helps someone, adjust your path locations accordingly.

On old versions of Debian and Ubuntu, you solved this by installing the Curl extension for PHP, and restarting the webserver. Assuming the webserver is Apache 2:

sudo apt-get install php5-curl
sudo service apache2 restart

On newer versions, the package name as changed:

sudo apt install php-curl

It's possible you'll need to install more:

sudo apt-get install curl libcurl3 libcurl3-dev;

$ch = curl_init('http://api.imgur.com/2/upload.xml'); //initialising our url

curl_setopt($ch, CURLOPT_MUTE, 1);

curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, FALSE);  //used for https headers 

curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, FALSE);  //used for https headers

curl_setopt($ch, CURLOPT_POST, 1);

curl_setopt($ch, CURLOPT_POSTFIELDS, urlencode($pvars));  
//the value we post

curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1); //waiting for reponse, default value in php is zero ie, curls normally do not wait for a response

curl_setopt($ch, CURLOPT_USERAGENT, 'Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.5) Gecko/20041107 Firefox/1.0'); 

$output = curl_exec($ch); //the real execution 
curl_close($ch);

echo $output;

Try this code. I am not sure about it. But i used it to send xml data to a remote url.

Experienced this on ubuntu 16.04 running PHP 7.1.14. To resolve,first put this in a script and execute. It will return true if curl is installed and enabled,otherwise, it will return false.

<?php
    var_dump(extension_loaded('curl'));
?>

If it returns false, run

sudo apt-get install php7.1-curl

And finally,

sudo service apache2 restart

After the restart, the script will return true and hopefully, your error should be resolved.