warning: mail() expects parameter 4 to be string - php

Question

I'm trying to use the below code to send mail, but got the below error
Doesn't mail() take in arrays for headers?
Warning: mail() expects parameter 4 to be string, array given in ../email.php on line 16
code :
<?php
$name = #trim(stripslashes($_POST['name']));
$from = #trim(stripslashes($_POST['email']));
$subject = #trim(stripslashes($_POST['subject']));
$message = #trim(stripslashes($_POST['message']));
$to = 'example#gmail.com';
$headers = array();
$headers[] = "MIME-Version: 1.0";
$headers[] = "Content-type: text/plain; charset=iso-8859-1";
$headers[] = "From: {$name} <{$from}>";
$headers[] = "Reply-To: <{$from}>";
$headers[] = "Subject: {$subject}";
$headers[] = "X-Mailer: PHP/".phpversion();
mail($to, $subject, $message, $headers);

Answer 1

PHP mail() need string $to, string $subject, string $message, string $headers
if you want to use an array for the headers
mail($to, $subject, $message, implode("\r\n", $headers));
else change your code in
$headers = "MIME-Version: 1.0\r\n";
$headers .= "Content-type: text/plain; charset=iso-8859-1\r\n";
$headers .= "From: {$name} <{$from}>\r\n";
$headers .= "Reply-To: <{$from}>\r\n";
$headers .= "Subject: {$subject}\r\n";
$headers .= "X-Mailer: PHP/".phpversion()."\r\n";
why \r\n (from mail() documentation)?
Multiple extra headers should be separated with a CRLF (\r\n) [...]
If messages are not received, try using a LF (\n) only. Some Unix mail
transfer agents (most notably » qmail) replace LF by CRLF
automatically (which leads to doubling CR if CRLF is used). This
should be a last resort, as it does not comply with » RFC 2822.
side note use "\r\n" and not '\r\n'

Answer 2

As the message says the 4th parameter ($additional_headers) should be a string. So you need to join the array elements:
$headers = implode("\r\n", $headers);
mail($to, $subject, $message, $headers);
From the documentation:
String to be inserted at the end of the email header.
This is typically used to add extra headers (From, Cc, and Bcc). Multiple extra headers should be separated with a CRLF (\r\n). If outside data are used to compose this header, the data should be sanitized so that no unwanted headers could be injected.

Answer 3

You make $headers to be a array, but it has to be a string! So just change these lines:
$headers = array();
$headers[] = "MIME-Version: 1.0";
$headers[] = "Content-type: text/plain; charset=iso-8859-1";
$headers[] = "From: {$name} <{$from}>";
$headers[] = "Reply-To: <{$from}>";
$headers[] = "Subject: {$subject}";
$headers[] = "X-Mailer: PHP/".phpversion();
to this and concatenate the strings together:
$headers = "";
$headers .= "MIME-Version: 1.0\r\n";
$headers .= "Content-type: text/plain; charset=iso-8859-1\r\n";
$headers .= "From: {$name} <{$from}>\r\n";
$headers .= "Reply-To: <{$from}>\r\n";
$headers .= "Subject: {$subject}\r\n";
$headers .= "X-Mailer: PHP/" . phpversion() . "\r\n";