wp_db->strip_invalid_text problem with NULL varchar(2) fields

[TiagoGouvea]

When I tried to save a record the udpdate fails and looking for the problem I found a possible error in wp_db.

In block :
"$converted_data = $this->strip_invalid_text( $data );
if ( $data !== $converted_data ) {"

If always return false to me, looking closer on strip_invalid_text method, I saw that a field seen to be different in that arrays. The field have null value but, it show value in the $data array as 'NU', because the field are a varchar(2), and then, it consider $data!=$converted_data, when it's not.

• I'm updating another field, but the query include the null field on the update again. I'm not changig that field value.

[pento]

Thank you for the bug report, @TiagoGouvea!

Could you provide a test case that I can use to reproduce this behaviour?

[TobiasBg]

Possibly related, as it deals with the same lines of code: #34482

[dd32]

Discussion happened in another ticket - https://core.trac.wordpress.org/ticket/34482#comment:6

@TiagoGouvea was passing a string to $wpdb->update() and then was filtering the query later to force 'NULL' to NULL.

@TiagoGouvea That's just not supported, and won't be in any way. In WordPress 4.4+ passing a literal NULL does work. If you need to support older versions, don't use $wpdb->update() and instead do $wpdb->update( "UPDATE .. SET field = NULL" );.