3v4l.org

run code in 300+ PHP versions simultaneously
<?php $str = '1 NM 2951-2 S Sodium: LN 144 mmol/L mmol/L 135-145 F 201402150533 2 NM 2823-3 S Potassium: LN 5.6 mmol/L mmol/L 3.5-5.5 H F 201402150533 3 NM 2075-0 S Chloride: LN 103 mmol/L mmol/L 95-110 F 201402150533'; echo preg_replace('/\b\d{12}\b(?!$)\K\s*/', '<br>', $str);

preferences:
25.22 ms | 404 KiB | 5 Q