$wpdb->insert inserting only f character in custom table

Question

I have made a quick $wpdb->insert function that adds content with an AJAX function.

The goal is to insert the form data into a table.

Here is my Javascript function calling the ajax:

$(".modal__form").submit(function(e){

            e.preventDefault();

            $.post(

                ajaxurl,
                {
                    'action': 'add_to_newsletter',
                    'param': $(this).serialize()
                },
                function(response){

                    if(response == 'success') {

                        $('.modal__form').hide();
                        $('.modal__box .text__success').show();
                    }
                }
            );

        });

The form data in headers can be printed as :

action: add_to_newsletter
param: firstname=FIRSTNAME&lastname=LASTNAME&email=EMAIL%40DOMAIN.COM&type=TYPE

On my function, I have this :

function add_to_newsletter() {

    global $wpdb;

    $table = $wpdb->prefix.'newsletter';
    $param = $_POST['param'];

    if($wpdb->insert($table, array(

        'firstname' => $param['firstname'],
        'lastname' => $param['lastname'],
        'email' => $param['email'],
        'ip' => $_SERVER['REMOTE_ADDR']

        ),
        array( '%s', '%s', '%s', '%s')
    )) {

        var_dump($wpdb);
        echo 'success';

    }
    else {

        $wpdb->print_error();
    }



    die();
}
add_action( 'wp_ajax_add_to_newsletter', 'add_to_newsletter' );
add_action( 'wp_ajax_nopriv_add_to_newsletter', 'add_to_newsletter' );

The problem is that I only got strange things on the database when posted.

Here is the var_dump() return.

"INSERT INTO 'actz_newsletter' ('firstname', 'lastname', 'email', 'ip') VALUES ('f', 'f', 'f', '::1')"

Anyone ever expected something similar? I am clueless about my research.

Answer 1

$_POST['param'] is a string, you can not treat it like an array. That's why only f characters are inserted.

You have two options, prepare data as an array in javascript or parse the string to array on the PHP side.

Sample code for 2nd option:

$table = $wpdb->prefix.'newsletter';

// 'firstname=FIRSTNAME&lastname=LASTNAME&email=EMAIL%40DOMAIN.COM&type=TYPE'
$input = explode( '&', $_POST['param'] );
$param = array_reduce( $input, function( &$carry, $item ) {
            $parts = explode('=', $item);
            $carry[ $parts[0] ] = urldecode( $parts[1] );
            return $carry;
        }, 
        array()
);