3v4l.org

run code in 300+ PHP versions simultaneously
<?php $arr = array(); $arr['b'] = 'book'; foreach($arr as $key=>$val) { print "key=>$key\n"; if(!isset($arr['a'])) $arr['a'] = 'apple'; } echo '<pre>'; print_r($arr);

preferences:
33.55 ms | 402 KiB | 5 Q