Enhancing this form with PHP and WordPress magic

custom WordPress form

<form action="#" method="POST" class="comment-form">
	<?php wp_nonce_field( 'faire-don', 'cagnotte-verif' ); ?>

	<div>
		<label for="don"><?php _e( 'Amount donation' ); ?></label>
		<input id="don" type="number" name="don" value="5" />
	</div>

	<input id="submit" type="submit" name="cagnote-don-envoi" id="submit" class="submit" value="<?php esc_attr_e( 'Submit', 'msk' ); ?>" />
</form>

functions.php

<?php function traitement_formulaire_don_cagnotte() {
	if ( ! isset( $_POST['cagnote-don-envoi'] ) || ! isset( $_POST['cagnotte-verif'] ) )  {
		return;
	}

	if ( ! wp_verify_nonce( $_POST['cagnotte-verif'], 'faire-don' ) ) {
		return;
	}

	// Process the form...
}
add_action( 'template_redirect', 'traitement_formulaire_don_cagnotte' );

#Let’s focus on the processing logic of the form: we leave the template to go to the functions.php file in order to process the data received.