A small script to be used as sendmail for debugging mailing functions in php.

sendmail.php

<?php

/**
 * @file
 *
 * Mock Sendmail
 *
 * A small script to be used as sendmail for debugging mailing functions in php.
 *
 * Usage:
 * php -d sendmail_path='php ./sendmail.php' email_sending_script.php
 *
 * Or you'd need to specify in php.ini the 'sendmail_path' as 'php FULL_PATH_TO/sendmail.php'.
 *
 * Then in PHP, use mail() normally. For example:
 * <code>
 * mail('email_to@gmail.com', 'Subject', "<p>A very long message</p>\n<p>Thanks</p>", ['X-User-Agent' => 'hello_php']);
 * </code>
 * 
 * To specify the JSON capture file for the specific call, you can add the capture filename:
 * <code>
 * mail(
 *   'email_to@gmail.com',
 *   'Subject',
 *   "<p>A very long message</p>\n<p>Thanks</p>",
 *   ['X-User-Agent' => 'hello_php'],
 *   '--capture-file="' . __DIR__ . '/email-call-123.json"',
 * );
 * </code>
 *
 * @see https://www.php.net/manual/en/function.mail.php
 * @see https://www.php.net/manual/en/mail.configuration.php
 */

// Allow script user to specify the path of the file to capture.
$options = getopt('', [
  'capture-file::',
]) + [
  'capture-file' => './mock-sendmail-capture.json',
];
$capture_filename = $options['capture-file'];

// Capture all the inputs.
$stdin = stream_get_contents(fopen('php://stdin', 'r'));
file_put_contents($capture_filename, json_encode([
  'argv' => $argv,
  'stdin' => $stdin,
], JSON_PRETTY_PRINT|JSON_PARTIAL_OUTPUT_ON_ERROR|JSON_UNESCAPED_UNICODE|JSON_UNESCAPED_SLASHES|JSON_UNESCAPED_LINE_TERMINATORS));