3v4l.org

run code in 200+ php & hhvm versions
```<?php \$a1 = array(a1,a2,a3,a4); \$result='"'.implode("','",\$a1).'"'; echo \$result;```
Output for 7.2.0
Warning: Use of undefined constant a1 - assumed 'a1' (this will throw an Error in a future version of PHP) in /in/ovelC on line 2 Warning: Use of undefined constant a2 - assumed 'a2' (this will throw an Error in a future version of PHP) in /in/ovelC on line 2 Warning: Use of undefined constant a3 - assumed 'a3' (this will throw an Error in a future version of PHP) in /in/ovelC on line 2 Warning: Use of undefined constant a4 - assumed 'a4' (this will throw an Error in a future version of PHP) in /in/ovelC on line 2 "a1','a2','a3','a4"
Output for 5.5.0 - 7.1.7
Notice: Use of undefined constant a1 - assumed 'a1' in /in/ovelC on line 2 Notice: Use of undefined constant a2 - assumed 'a2' in /in/ovelC on line 2 Notice: Use of undefined constant a3 - assumed 'a3' in /in/ovelC on line 2 Notice: Use of undefined constant a4 - assumed 'a4' in /in/ovelC on line 2 "a1','a2','a3','a4"
Output for 4.3.0 - 5.4.45
"a1','a2','a3','a4"