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run code in 300+ PHP versions simultaneously
<?php $a=array('0.txt','1.txt','2.txt','3.txt'); $n=(int)current(explode('.',end($a))); echo $n+=1; $a[]=$n.'txt'; $n=(int)current(explode('.',end($a))); echo $n+=1; $a[]=$n.'txt'; $n=(int)current(explode('.',end($a))); echo $n+=1; $a[]=$n.'txt'; ?>
Output for 4.3.0 - 4.3.11, 4.4.0 - 4.4.9, 5.0.0 - 5.0.4, 5.1.0 - 5.1.6, 5.2.0 - 5.2.17, 5.3.0 - 5.3.29, 5.4.0 - 5.4.45, 5.5.0 - 5.5.37, 5.6.0 - 5.6.28, 7.0.0 - 7.0.20, 7.1.0 - 7.1.20, 7.2.29 - 7.2.33, 7.3.12 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.27, 8.2.0 - 8.2.17, 8.3.0 - 8.3.4
456
Output for 5.0.5
Fatal error: Only variables can be passed by reference in /in/m1H7J on line 5
Process exited with code 255.

preferences:
262.14 ms | 401 KiB | 345 Q