How can I send an email using PHP?

It’s possible using PHP’s mail() function. Remember the mail function will not work on a local server.

Reference:

mail

You could also use PHPMailer class at https://github.com/PHPMailer/PHPMailer .
It allows you to use the mail function or use an smtp server transparently. It also handles HTML based emails and attachments so you don’t have to write your own implementation.
The class is stable and it is used by many other projects like Drupal, SugarCRM, Yii, and Joomla!
Here is an example from the page above:
isSMTP(); // Set mailer to use SMTP
$mail->Host = ‘smtp1.example.com;smtp2.example.com’; // Specify main and backup SMTP servers
$mail->SMTPAuth = true; // Enable SMTP authentication
$mail->Username = ‘[email protected]’; // SMTP username
$mail->Password = ‘secret’; // SMTP password
$mail->SMTPSecure = ‘tls’; // Enable encryption, ‘ssl’ also accepted

$mail->From = ‘[email protected]’;
$mail->FromName = ‘Mailer’;
$mail->addAddress(‘[email protected]’, ‘Joe User’); // Add a recipient
$mail->addAddress(‘[email protected]’); // Name is optional
$mail->addReplyTo(‘[email protected]’, ‘Information’);
$mail->addCC(‘[email protected]’);
$mail->addBCC(‘[email protected]’);

$mail->WordWrap = 50; // Set word wrap to 50 characters
$mail->addAttachment(‘/var/tmp/file.tar.gz’); // Add attachments
$mail->addAttachment(‘/tmp/image.jpg’, ‘new.jpg’); // Optional name
$mail->isHTML(true); // Set email format to HTML

$mail->Subject = ‘Here is the subject’;
$mail->Body = ‘This is the HTML message body in bold!‘;
$mail->AltBody = ‘This is the body in plain text for non-HTML mail clients’;

if(!$mail->send()) {
echo ‘Message could not be sent.’;
echo ‘Mailer Error: ‘ . $mail->ErrorInfo;
} else {
echo ‘Message has been sent’;
}