3v4l.org

run code in 300+ PHP versions simultaneously
<?php $array = [1, 1, 2, 3, 4, 5, 6, 7, 9, 9, 10]; $result = []; foreach ($array as $index => $value) { if (!isset($result[$value])) { $result[$value] = $index; } else { $result[$value] .= ",$index"; } } var_export(array_values($result));
Output for 7.3.0 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.33, 8.2.0 - 8.2.29, 8.3.0 - 8.3.4, 8.3.6 - 8.3.26, 8.4.1 - 8.4.13
array ( 0 => '0,1', 1 => 2, 2 => 3, 3 => 4, 4 => 5, 5 => 6, 6 => 7, 7 => '8,9', 8 => 10, )
Output for 8.3.5
Warning: PHP Startup: Unable to load dynamic library 'sodium.so' (tried: /usr/lib/php/8.3.5/modules/sodium.so (libsodium.so.23: cannot open shared object file: No such file or directory), /usr/lib/php/8.3.5/modules/sodium.so.so (/usr/lib/php/8.3.5/modules/sodium.so.so: cannot open shared object file: No such file or directory)) in Unknown on line 0 array ( 0 => '0,1', 1 => 2, 2 => 3, 3 => 4, 4 => 5, 5 => 6, 6 => 7, 7 => '8,9', 8 => 10, )

preferences:
133.37 ms | 408 KiB | 5 Q