Missing error check in convert_smilies() can cause PHP Fatal error

[Ov3rfly]

A client website caused PHP Fatal error, tracked it down and came to this:

PHP Fatal error:  Uncaught TypeError: count(): Argument #1 ($value) must be of type Countable|array, bool given in .. wp-includes/formatting.php:3507

Which is this code:

// HTML loop taken from texturize function, could possible be consolidated.
$textarr = preg_split( '/(<.*>)/U', $text, -1, PREG_SPLIT_DELIM_CAPTURE ); // Capture the tags as well as in between.
$stop    = count( $textarr ); // Loop stuff.

The error occurs if preg_split() returns false and that is used as argument for count().

Since false is a valid return value here as described in PHP documentation, there should be a check for this case.

The problem is somehow related to size of $text where PHP interally obviously can't handle the data (any more).

Attached exported simplified WXR testcase. If you shorten the XXX part, the error might not appear any more.

Note: This kind of problem caused a PHP Warning with PHP 7.x but causes a PHP Fatal error since PHP 8.x

[Ov3rfly]

WXR testcase

[jorbin]

Optimistically putting this in the 6.5 milestone.

In my eyes, the biggest question is what should be expected when the regex fails. Perhaps throw an error but then continue without converted smilies?

[jrf]

I have a feeling this is a duplicate of #51019...

[Ov3rfly]

@jorbin Suggested fix:

// HTML loop taken from texturize function, could possible be consolidated.
$textarr = preg_split( '/(<.*>)/U', $text, -1, PREG_SPLIT_DELIM_CAPTURE ); // Capture the tags as well as in between.
if ( $textarr === false ) {
	return $text;	// do nothing
}
$stop    = count( $textarr ); // Loop stuff.

Would also suggest an earlier milestone as 6.5, otherwise the issue gets burried (again).

@jrf Good find, seems like the same issue is described there, did search but maybe not 3 years back. Would not call it php80 related though as the missing check for false is the real problem here, not the change from Warning to Fatal since PHP 8.x.

[Ov3rfly]

@jrf On second thought the issue actually is also php80 related as it can cause a Fatal error and disruption in front end. A fix probably should be backported to all WordPress branches which claim PHP 8.x compatibility.

[jorbin]

Duplicate of #51019.

Agree with @jrf, this is a duplicate. Going to consolidate the discussion there