This happens in serialize_block_attributes
, the docblock explains why:
/**
...
* The serialized result is a JSON-encoded string, with unicode escape sequence
* substitution for characters which might otherwise interfere with embedding
* the result in an HTML comment.
...
*/
So this is done as an encoding measure to avoid attributes accidentally closing a HTML comment and breaking the format of the document.
Without this, a HTML comment inside a block attribute would break the block and the rest of the content afterwards.
But How Do I Stop The Mangling?!!!
No, it isn’t mangled. It’s just encoding certain characters by replacing them with unicode escaped versions to prevent breakage.
Proof 1
Lets take the original code block from the question, and add the following fixes:
- Wrap all in
<pre>
tags - Use
esc_html
so we can see the tags properly - Fix the
printf
by removingvar_dump
and usingvar_export
with the second parameter so it returns rather than outputs - Add a final test case where we re-parse and re-serialize 10 times to compare the final result with the original
function reparse_reserialize( string $content, int $loops = 10 ) : string {
$final_content = $content;
for ($x = 0; $x <= $loops; $x++) {
$blocks = parse_blocks( $final_content );
$final_content = serialize_blocks( $blocks );
}
return $final_content;
}
add_action(
'wp',
function() {
$p = get_post( 1 );
echo '<p>Original content:</p>';
echo '<pre>' . esc_html( var_export( $p->post_content, true ) ) . '</pre>';
$final = reparse_reserialize( $p->post_content );
echo '<p>10 parse and serialize loops later:</p>';
echo '<pre>' . esc_html( var_export( $final, true ) ) . '</pre>';
echo '<hr/>';
},
PHP_INT_MAX
);
Running that, we see that the content survived the process of being parsed and re-serialized 10 times. If mangling was occuring we would see progressively greater mangling occur
Proof 2
If we take the mangled markup:
\u003ch3\u003eWhat types of accommodation are available in xxxx?\u003c\/h3\u003e
Turn it into a JSON string, then decode it:
$json = '"\u003ch3\u003eWhat types of accommodation are available in xxxx?\u003c\/h3\u003e"';
echo '<pre>' . esc_html( json_decode( $json ) ) . '</pre>';
We get the original HTML:
<h3>What types of accommodation are available in xxxx?</h3>
So no mangling has taken place.
Summary
There is no mangling or corruption. It’s just encoding the <
and >
to prevent breakage. JSON processors handle the unicode escape characters just fine.
If you are seeing these encoded characters in the block editor, then that is a bug, either in the block, or the ACF plugin. You should report it as such