wp-includes/formatting.php:5479Normalizes EOL characters and strips duplicate whitespace.
$strstringstringfunction normalize_whitespace( $str ) { $str = trim( $str ); $str = str_replace( "\r", "\n", $str ); $str = preg_replace( array( '/\n+/', '/[ \t]+/' ), array( "\n", ' ' ), $str ); return $str;}Introduced in 2.7.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/formatting.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.