wp-admin/includes/class-wp-site-health.php:1193Tests if there's an active PHP session that can affect loopback requests.
array public function get_test_php_sessions() { $result = array( 'label' => __( 'No PHP sessions detected' ), 'status' => 'good', 'badge' => array( 'label' => __( 'Performance' ), 'color' => 'blue', ), 'description' => sprintf( '<p>%s</p>', sprintf( /* translators: 1: session_start(), 2: session_write_close() */ __( 'PHP sessions created by a %1$s function call may interfere with REST API and loopback requests. An active session should be closed by %2$s before making any HTTP requests.' ), '<code>session_start()</code>', '<code>session_write_close()</code>' ) ), 'test' => 'php_sessions', ); if ( function_exists( 'session_status' ) && PHP_SESSION_ACTIVE === session_status() ) { $result['status'] = 'critical'; $result['label'] = __( 'An active PHP session was detected' ); $result['description'] = sprintf( '<p>%s</p>', sprintf( /* translators: 1: session_start(), 2: session_write_close() */ __( 'A PHP session was created by a %1$s function call. This interferes with REST API and loopback requests. The session should be closed by %2$s before making any HTTP requests.' ), '<code>session_start()</code>', '<code>session_write_close()</code>' ) ); } return $result; }Introduced in 5.5.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-admin/includes/class-wp-site-health.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.