wp-includes/class-wpdb.php:2411Generates and returns a placeholder escape string for use in queries returned by ::prepare().
string public function placeholder_escape() { static $placeholder; if ( ! $placeholder ) { // Old WP installs may not have AUTH_SALT defined. $salt = defined( 'AUTH_SALT' ) && AUTH_SALT ? AUTH_SALT : (string) rand(); $placeholder = '{' . hash_hmac( 'sha256', uniqid( $salt, true ), $salt ) . '}'; } /* * Add the filter to remove the placeholder escaper. Uses priority 0, so that anything * else attached to this filter will receive the query with the placeholder string removed. */ if ( false === has_filter( 'query', array( $this, 'remove_placeholder_escape' ) ) ) { add_filter( 'query', array( $this, 'remove_placeholder_escape' ), 0 ); } return $placeholder; }Introduced in 4.8.3. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/class-wpdb.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.