3v4l.org

run code in 500+ PHP versions simultaneously
<?php $text = ".a {\r\n // rules\r\n}\r\n\r\n.a-b,\r\n.a-b .b, .a-b.s\r\n.x .y, .x {\r\n // rules\r\n}\r\n\r\n@a {\r\n // rules\r\n}\r\n\r\n@k {\r\n // rules\r\n}"; echo preg_replace('~(?:\G(?!\A)|^[@.])[^{]*?\K\s+~m', ' ', $text);
Output for 7.3.0 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.34, 8.2.0 - 8.2.34, 8.3.0 - 8.3.35, 8.4.1 - 8.4.26, 8.5.0 - 8.5.11
.a { // rules } .a-b, .a-b .b, .a-b.s .x .y, .x { // rules } @a { // rules } @k { // rules }
preferences:
32.07 ms | 1137 KiB | 7 Q