Online PHP editor | output for AbBH1

<?php function my_cb( $a ) { return 'AAA' . PHP_EOL . $a . 'BBB' . PHP_EOL; } function my_cb2( $a ) { if ( $a === 'XXX' ) { return false; } if ( $a === '' ) { $a = 'EMPTY'; } return 'CCC' . PHP_EOL . $a . 'DDD' . PHP_EOL; } ob_start( 'my_cb', 0 ); ob_start( 'my_cb2', 0 ); echo "XXX"; ob_flush(); #var_dump( ob_get_status( true ) ); echo "ONE" . PHP_EOL; ob_flush(); echo "TWO" . PHP_EOL; ob_flush();