Creating config file for all define in php

config.php

<?php
// creating associate array with all parameters
$config = [
    'param_1' => 'value_1'
    'param_2' => 'value_2'
    'param_3' => 'value_3'
];



// function to comfortable using variables in different places, default nutt predefine
function getConfig($key, $default = null) {
    if(isset($config[$key])) {
        return $config[$key];
    }
    return $default;
}

// example
        if($xml->ResponseCode == 'NoError') {       // successful registration
//           2 param available in getConfig, 2nd not important
            mail(getConfig('param_1', 'if haven\'t first param use this one'),"something_data", $body, $headers);
            mail($_POST['Email'],"somethig_data", file_get_contents('email.html'), $headers);
            header("Location: http://coolsculpting.previenthealthmedia.com/thankyou.html");
            exit();
        }

?>