Sends an email, similar to PHP’s mail function.

A true return value does not automatically mean that the user received the
email successfully. It just only means that the method used was able to
process the request without any errors.

The default content type is `text/plain` which does not allow using HTML.
However, you can set the content type of the email by using the
{@see ‘wp_mail_content_type’} filter.

The default charset is based on the charset used on the blog. The charset can
be set using the {@see ‘wp_mail_charset’} filter.

function wp_mail( $to, $subject, $message, $headers = '', $attachments = array() ) {
		// Compact the input, apply the filters, and extract them back out.

		/**
		 * Filters the wp_mail() arguments.
		 *
		 * @since 2.2.0
		 *
		 * @param array $args {
		 *     Array of the `wp_mail()` arguments.
		 *
		 *     @type string|string[] $to          Array or comma-separated list of email addresses to send message.
		 *     @type string          $subject     Email subject.
		 *     @type string          $message     Message contents.
		 *     @type string|string[] $headers     Additional headers.
		 *     @type string|string[] $attachments Paths to files to attach.
		 * }
		 */
		$atts = apply_filters( 'wp_mail', compact( 'to', 'subject', 'message', 'headers', 'attachments' ) );

		/**
		 * Filters whether to preempt sending an email.
		 *
		 * Returning a non-null value will short-circuit {@see wp_mail()}, returning
		 * that value instead. A boolean return value should be used to indicate whether
		 * the email was successfully sent.
		 *
		 * @since 5.7.0
		 *
		 * @param null|bool $return Short-circuit return value.
		 * @param array     $atts {
		 *     Array of the `wp_mail()` arguments.
		 *
		 *     @type string|string[] $to          Array or comma-separated list of email addresses to send message.
		 *     @type string          $subject     Email subject.
		 *     @type string          $message     Message contents.
		 *     @type string|string[] $headers     Additional headers.
		 *     @type string|string[] $attachments Paths to files to attach.
		 * }
		 */
		$pre_wp_mail = apply_filters( 'pre_wp_mail', null, $atts );

		if ( null !== $pre_wp_mail ) {
			return $pre_wp_mail;
		}

		if ( isset( $atts['to'] ) ) {
			$to = $atts['to'];
		}

		if ( ! is_array( $to ) ) {
			$to = explode( ',', $to );
		}

		if ( isset( $atts['subject'] ) ) {
			$subject = $atts['subject'];
		}

		if ( isset( $atts['message'] ) ) {
			$message = $atts['message'];
		}

		if ( isset( $atts['headers'] ) ) {
			$headers = $atts['headers'];
		}

		if ( isset( $atts['attachments'] ) ) {
			$attachments = $atts['attachments'];
		}

		if ( ! is_array( $attachments ) ) {
			$attachments = explode( "n", str_replace( "rn", "n", $attachments ) );
		}
		global $phpmailer;

		// (Re)create it, if it's gone missing.
		if ( ! ( $phpmailer instanceof PHPMailerPHPMailerPHPMailer ) ) {
			require_once ABSPATH . WPINC . '/PHPMailer/PHPMailer.php';
			require_once ABSPATH . WPINC . '/PHPMailer/SMTP.php';
			require_once ABSPATH . WPINC . '/PHPMailer/Exception.php';
			$phpmailer = new PHPMailerPHPMailerPHPMailer( true );

			$phpmailer::$validator = static function ( $email ) {
				return (bool) is_email( $email );
			};
		}

		// Headers.
		$cc       = array();
		$bcc      = array();
		$reply_to = array();

		if ( empty( $headers ) ) {
			$headers = array();
		} else {
			if ( ! is_array( $headers ) ) {
				// Explode the headers out, so this function can take
				// both string headers and an array of headers.
				$tempheaders = explode( "n", str_replace( "rn", "n", $headers ) );
			} else {
				$tempheaders = $headers;
			}
			$headers = array();

			// If it's actually got contents.
			if ( ! empty( $tempheaders ) ) {
				// Iterate through the raw headers.
				foreach ( (array) $tempheaders as $header ) {
					if ( strpos( $header, ':' ) === false ) {
						if ( false !== stripos( $header, 'boundary=' ) ) {
							$parts    = preg_split( '/boundary=/i', trim( $header ) );
							$boundary = trim( str_replace( array( "'", '"' ), '', $parts[1] ) );
						}
						continue;
					}
					// Explode them out.
					list( $name, $content ) = explode( ':', trim( $header ), 2 );

					// Cleanup crew.
					$name    = trim( $name );
					$content = trim( $content );

					switch ( strtolower( $name ) ) {
						// Mainly for legacy -- process a "From:" header if it's there.
						case 'from':
							$bracket_pos = strpos( $content, ' 0 ) {
									$from_name = substr( $content, 0, $bracket_pos );
									$from_name = str_replace( '"', '', $from_name );
									$from_name = trim( $from_name );
								}

								$from_email = substr( $content, $bracket_pos + 1 );
								$from_email = str_replace( '>', '', $from_email );
								$from_email = trim( $from_email );

								// Avoid setting an empty $from_email.
							} elseif ( '' !== trim( $content ) ) {
								$from_email = trim( $content );
							}
							break;
						case 'content-type':
							if ( strpos( $content, ';' ) !== false ) {
								list( $type, $charset_content ) = explode( ';', $content );
								$content_type                   = trim( $type );
								if ( false !== stripos( $charset_content, 'charset=' ) ) {
									$charset = trim( str_replace( array( 'charset=', '"' ), '', $charset_content ) );
								} elseif ( false !== stripos( $charset_content, 'boundary=' ) ) {
									$boundary = trim( str_replace( array( 'BOUNDARY=', 'boundary=', '"' ), '', $charset_content ) );
									$charset  = '';
								}

								// Avoid setting an empty $content_type.
							} elseif ( '' !== trim( $content ) ) {
								$content_type = trim( $content );
							}
							break;
						case 'cc':
							$cc = array_merge( (array) $cc, explode( ',', $content ) );
							break;
						case 'bcc':
							$bcc = array_merge( (array) $bcc, explode( ',', $content ) );
							break;
						case 'reply-to':
							$reply_to = array_merge( (array) $reply_to, explode( ',', $content ) );
							break;
						default:
							// Add it to our grand headers array.
							$headers[ trim( $name ) ] = trim( $content );
							break;
					}
				}
			}
		}

		// Empty out the values that may be set.
		$phpmailer->clearAllRecipients();
		$phpmailer->clearAttachments();
		$phpmailer->clearCustomHeaders();
		$phpmailer->clearReplyTos();
		$phpmailer->Body    = '';
		$phpmailer->AltBody = '';

		// Set "From" name and email.

		// If we don't have a name from the input headers.
		if ( ! isset( $from_name ) ) {
			$from_name = 'WordPress';
		}

		/*
		 * If we don't have an email from the input headers, default to wordpress@$sitename
		 * Some hosts will block outgoing mail from this address if it doesn't exist,
		 * but there's no easy alternative. Defaulting to admin_email might appear to be
		 * another option, but some hosts may refuse to relay mail from an unknown domain.
		 * See https://core.trac.wordpress.org/ticket/5007.
		 */
		if ( ! isset( $from_email ) ) {
			// Get the site domain and get rid of www.
			$sitename   = wp_parse_url( network_home_url(), PHP_URL_HOST );
			$from_email = 'wordpress@';

			if ( null !== $sitename ) {
				if ( 'www.' === substr( $sitename, 0, 4 ) ) {
					$sitename = substr( $sitename, 4 );
				}

				$from_email .= $sitename;
			}
		}

		/**
		 * Filters the email address to send from.
		 *
		 * @since 2.2.0
		 *
		 * @param string $from_email Email address to send from.
		 */
		$from_email = apply_filters( 'wp_mail_from', $from_email );

		/**
		 * Filters the name to associate with the "from" email address.
		 *
		 * @since 2.3.0
		 *
		 * @param string $from_name Name associated with the "from" email address.
		 */
		$from_name = apply_filters( 'wp_mail_from_name', $from_name );

		try {
			$phpmailer->setFrom( $from_email, $from_name, false );
		} catch ( PHPMailerPHPMailerException $e ) {
			$mail_error_data                             = compact( 'to', 'subject', 'message', 'headers', 'attachments' );
			$mail_error_data['phpmailer_exception_code'] = $e->getCode();

			/** This filter is documented in wp-includes/pluggable.php */
			do_action( 'wp_mail_failed', new WP_Error( 'wp_mail_failed', $e->getMessage(), $mail_error_data ) );

			return false;
		}

		// Set mail's subject and body.
		$phpmailer->Subject = $subject;
		$phpmailer->Body    = $message;

		// Set destination addresses, using appropriate methods for handling addresses.
		$address_headers = compact( 'to', 'cc', 'bcc', 'reply_to' );

		foreach ( $address_headers as $address_header => $addresses ) {
			if ( empty( $addresses ) ) {
				continue;
			}

			foreach ( (array) $addresses as $address ) {
				try {
					// Break $recipient into name and address parts if in the format "Foo ".
					$recipient_name = '';

					if ( preg_match( '/(.*)/', $address, $matches ) ) {
						if ( count( $matches ) == 3 ) {
							$recipient_name = $matches[1];
							$address        = $matches[2];
						}
					}

					switch ( $address_header ) {
						case 'to':
							$phpmailer->addAddress( $address, $recipient_name );
							break;
						case 'cc':
							$phpmailer->addCc( $address, $recipient_name );
							break;
						case 'bcc':
							$phpmailer->addBcc( $address, $recipient_name );
							break;
						case 'reply_to':
							$phpmailer->addReplyTo( $address, $recipient_name );
							break;
					}
				} catch ( PHPMailerPHPMailerException $e ) {
					continue;
				}
			}
		}

		// Set to use PHP's mail().
		$phpmailer->isMail();

		// Set Content-Type and charset.

		// If we don't have a content-type from the input headers.
		if ( ! isset( $content_type ) ) {
			$content_type = 'text/plain';
		}

		/**
		 * Filters the wp_mail() content type.
		 *
		 * @since 2.3.0
		 *
		 * @param string $content_type Default wp_mail() content type.
		 */
		$content_type = apply_filters( 'wp_mail_content_type', $content_type );

		$phpmailer->ContentType = $content_type;

		// Set whether it's plaintext, depending on $content_type.
		if ( 'text/html' === $content_type ) {
			$phpmailer->isHTML( true );
		}

		// If we don't have a charset from the input headers.
		if ( ! isset( $charset ) ) {
			$charset = get_bloginfo( 'charset' );
		}

		/**
		 * Filters the default wp_mail() charset.
		 *
		 * @since 2.3.0
		 *
		 * @param string $charset Default email charset.
		 */
		$phpmailer->CharSet = apply_filters( 'wp_mail_charset', $charset );

		// Set custom headers.
		if ( ! empty( $headers ) ) {
			foreach ( (array) $headers as $name => $content ) {
				// Only add custom headers not added automatically by PHPMailer.
				if ( ! in_array( $name, array( 'MIME-Version', 'X-Mailer' ), true ) ) {
					try {
						$phpmailer->addCustomHeader( sprintf( '%1$s: %2$s', $name, $content ) );
					} catch ( PHPMailerPHPMailerException $e ) {
						continue;
					}
				}
			}

			if ( false !== stripos( $content_type, 'multipart' ) && ! empty( $boundary ) ) {
				$phpmailer->addCustomHeader( sprintf( 'Content-Type: %s; boundary="%s"', $content_type, $boundary ) );
			}
		}

		if ( ! empty( $attachments ) ) {
			foreach ( $attachments as $attachment ) {
				try {
					$phpmailer->addAttachment( $attachment );
				} catch ( PHPMailerPHPMailerException $e ) {
					continue;
				}
			}
		}

		/**
		 * Fires after PHPMailer is initialized.
		 *
		 * @since 2.2.0
		 *
		 * @param PHPMailer $phpmailer The PHPMailer instance (passed by reference).
		 */
		do_action_ref_array( 'phpmailer_init', array( &$phpmailer ) );

		$mail_data = compact( 'to', 'subject', 'message', 'headers', 'attachments' );

		// Send!
		try {
			$send = $phpmailer->send();

			/**
			 * Fires after PHPMailer has successfully sent an email.
			 *
			 * The firing of this action does not necessarily mean that the recipient(s) received the
			 * email successfully. It only means that the `send` method above was able to
			 * process the request without any errors.
			 *
			 * @since 5.9.0
			 *
			 * @param array $mail_data {
			 *     An array containing the email recipient(s), subject, message, headers, and attachments.
			 *
			 *     @type string[] $to          Email addresses to send message.
			 *     @type string   $subject     Email subject.
			 *     @type string   $message     Message contents.
			 *     @type string[] $headers     Additional headers.
			 *     @type string[] $attachments Paths to files to attach.
			 * }
			 */
			do_action( 'wp_mail_succeeded', $mail_data );

			return $send;
		} catch ( PHPMailerPHPMailerException $e ) {
			$mail_data['phpmailer_exception_code'] = $e->getCode();

			/**
			 * Fires after a PHPMailerPHPMailerException is caught.
			 *
			 * @since 4.4.0
			 *
			 * @param WP_Error $error A WP_Error object with the PHPMailerPHPMailerException message, and an array
			 *                        containing the mail recipient, subject, message, headers, and attachments.
			 */
			do_action( 'wp_mail_failed', new WP_Error( 'wp_mail_failed', $e->getMessage(), $mail_data ) );

			return false;
		}
	}
endif;

if ( ! function_exists( 'wp_authenticate' ) ) :
	/**
	 * Authenticates a user, confirming the login credentials are valid.
	 *
	 * @since 2.5.0
	 * @since 4.5.0 `$username` now accepts an email address.
	 *
	 * @param string $username User's username or email address.
	 * @param string $password User's password.
	 * @return WP_User|WP_Error WP_User object if the credentials are valid,
	 *                          otherwise WP_Error.
	 */