[justlevine]

What?

This PR fixes an issue in gutenberg_render_layout_support_flag() where a float type is passed into expode() which requires a string.

Why?

While this issue was surfaced by PHPStan (via #66693) it can be remediated independently as part of #66598

How?

Testing Instructions

Testing Instructions for Keyboard

Screenshots or screencast

Before	After

[carolinan]

Also needs updating in https://github.com/WordPress/wordpress-develop/blob/trunk/src/wp-includes/block-supports/layout.php#L620

[westonruter]

🤖 Comment by Claude Opus 5.5

trunk was merged in. The column-span logic has since moved from gutenberg_render_layout_support_flag() to gutenberg_get_child_layout_style_rules(), so the merge conflict was resolved by applying the cast there. A backport changelog entry was also added for WordPress/wordpress-develop#14862, which applies the same cast in wp_get_child_layout_style_rules() in core, along with three related PHPStan fixes, under Core-65817.

[github-actions]

🤖 PR meta 🤖

🎉 Props

If you're merging code through a pull request on GitHub, copy and paste the following into the bottom of the merge commit message.

Co-authored-by: justlevine <justlevine@git.wordpress.org>
Co-authored-by: westonruter <westonruter@git.wordpress.org>
Co-authored-by: carolinan <poena@git.wordpress.org>

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[westonruter]

🤖 Comment by Claude Opus 5.5

For context on the code being changed in gutenberg_get_child_layout_style_rules():

When a grid child has a columnSpan or columnStart and its parent grid is responsive (it has a minimumColumnWidth, or no fixed columnCount), the grid loses columns as its container narrows. Once there are fewer columns than the child spans or starts at, its placement has to be reset, so a container query is emitted, e.g.:

@container (max-width: 25.5rem) { .wp-container-content-xyz { grid-column: 1/-1; grid-row: auto; } }

To compute that width, the minimum column width (default 12rem) is split into a number and a unit:

$parent_column_width = $minimum_column_width ? $minimum_column_width : '12rem'; // '12rem'
$parent_column_value = floatval( $parent_column_width );                       // 12.0
$parent_column_unit  = explode( (string) $parent_column_value, $parent_column_width ); // explode( '12', '12rem' ) → [ '', 'rem' ]

The original string is split on the number, so the second element is the unit. Without a second element, the width is treated as mangled and reset to 12rem; a unit other than px, rem, or em falls back to rem. The width is then cols × value + (cols − 1) × gap, with a gap of 24 for px and 1.5 otherwise, subject to a minimum.

The (string) cast in this PR does not change behavior: explode() requires a string separator, and the cast does exactly what PHP's implicit conversion of the float did ((string) 12.0 is '12', and since PHP 8 this is locale-independent). It only makes the conversion explicit, which resolves the PHPStan argument.type error.

That said, the parsing itself, which this PR does not change, is fragile. Since the number is re-stringified before splitting, some valid values do not round-trip:

Input	floatval()	Separator	explode() result	Outcome
12rem	12.0	12	['', 'rem']	✅ 12rem
0.5em	0.5	0.5	['', 'em']	✅ 0.5em
1.50rem	1.5	1.5	['', '0rem']	⚠️ unit 0rem is invalid and falls back to rem, so 1.5rem is correct only by luck
.5em	0.5	0.5	['.5em']	❌ treated as mangled and reset to 12rem
10.0px	10.0	10	['', '.0px']	❌ unit .0px is invalid and falls back to rem, so 10px becomes 10rem

Matching with a regular expression, such as /^(\d*\.?\d+)(px|r?em)$/, similar to what gutenberg_get_typography_value_and_unit() now does, would be more robust. Since that is a behavior change, and wp_get_child_layout_style_rules() in core has the same code, it would be better handled in a separate PR and Trac ticket than in this PHPStan fix.

[westonruter]

Also needs updating in https://github.com/WordPress/wordpress-develop/blob/trunk/src/wp-includes/block-supports/layout.php#L620

Applied in WordPress/wordpress-develop#14862