Adding is_countable() check to custom-header.php

[ianbelanger]

Updating a single instance of count() in show_header_selector()

if ( count( $var ) > 0 ) {
        // Do something.
}

with is_countable()

if ( is_countable( $var ) && count( $var ) > 0 ) {
        // Do something.
}

in the custom-header.php file, in order to avoid warnings in PHP 7.2

[ianbelanger]

Updated custom-header.php with new is_countable() function

[jrf]

LGTM

[jrf]

You may also want to add a is_iterable() wrapper around the foreach() just below within the same function or move the whole block of code below within the if ( is_countable() & count() > 1 ) {} wrapper.

https://core.trac.wordpress.org/browser/trunk/src/wp-admin/custom-header.php#L295

[ianbelanger]

@jrf I was going to work on the is_countable() instances first, but I think it does make sense to do them both in the same diff. I will update the diff and re-upload. Thanks for the input!

[ianbelanger]

Updated diff to move foreach inside is_countable() condition

[netweb]

Related: #44123 - Utilize is_countable() and is_iterable() Polyfills

[johnbillion]

Thanks for your patch @ianbelanger.

I don't believe this is appropriate use of is_countable(). If a bug is introduced elsewhere which results in $headers being set to a non-countable value (for example via the return value of get_uploaded_header_images()), it's not a good idea to mask it via logic such as this. This is the reason that PHP now triggers warnings when attempting to count un-countable values since PHP 7.2.

See 44123#comment:11.

[desrosj]

Moving all tickets in 4.9.7 to 4.9.8.

[desrosj]

Looked this over. Agree that this instance of count() should not be updated.

Breaking it down, $headers could be of a type that is not countable, but only if the $_wp_default_headers global is overridden. In this scenario, an error should be thrown to indicate improper usage of $_wp_default_headers.