php opening & closing tags break code blocks

With a recent update, some of my code blocks broke: it closed the php shortcode automatically when there were multiple php opening and closing tags in the snippet.

Example:

[php]
add_action( 'wpo_wcpdf_after_order_data', 'wpo_wcpdf_due_date', 10, 2 );
function wpo_wcpdf_due_date ($template_type, $order) {
	if ($template_type == 'invoice') { // put due date only on invoice
		$invoice_date = get_post_meta( $order->id, '_wcpdf_invoice_date', true );
		$due_date = date_i18n( get_option( 'date_format' ), strtotime( $invoice_date . ' + 14 days') );
		?>
		<tr class="due-date">
			<th>Due Date:</th>
			<td><?php echo $due_date; ?></td>
		</tr>
		<?php
	}
}
[/php]

would save as (note the small but significant change in the first line):

[php][/php]
add_action( 'wpo_wcpdf_after_order_data', 'wpo_wcpdf_due_date', 10, 2 );
function wpo_wcpdf_due_date ($template_type, $order) {
	if ($template_type == 'invoice') { // put due date only on invoice
		$invoice_date = get_post_meta( $order->id, '_wcpdf_invoice_date', true );
		$due_date = date_i18n( get_option( 'date_format' ), strtotime( $invoice_date . ' + 14 days') );
		?>
		<tr class="due-date">
			<th>Due Date:</th>
			<td><?php echo $due_date; ?></td>
		</tr>
		<?php
	}
}
[/php]

This could be fixed by doing:

[php]
<?php
add_action( 'wpo_wcpdf_after_order_data', 'wpo_wcpdf_due_date', 10, 2 );
function wpo_wcpdf_due_date ($template_type, $order) {
	if ($template_type == 'invoice') { // put due date only on invoice
		$invoice_date = get_post_meta( $order->id, '_wcpdf_invoice_date', true );
		$due_date = date_i18n( get_option( 'date_format' ), strtotime( $invoice_date . ' + 14 days') );
		?>
		<tr class="due-date">
			<th>Due Date:</th>
			<td><?php echo $due_date; ?></td>
		</tr>
		<?php
	}
}
?>
[/php]

but that’s not what I want because I don’t want my customers to put the php tags in there theme functions (when blindly copy pasting).

Is there any other way to prevent this? Is this a bug or a feature?

https://wordpress.org/plugins/syntaxhighlighter/