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<?php $a = ['name'=>'a','age'=>'b','city'=>'c']; $new_array = array_merge($a, ['add' => $a]); print_r($new_array);
Output for 5.6.38, 7.1.0 - 7.1.33, 7.2.0 - 7.2.33, 7.3.0 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.28, 8.2.0 - 8.2.19, 8.3.0 - 8.3.4, 8.3.6 - 8.3.7
Array ( [name] => a [age] => b [city] => c [add] => Array ( [name] => a [age] => b [city] => c ) )
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 ( [name] => a [age] => b [city] => c [add] => Array ( [name] => a [age] => b [city] => c ) )

preferences:
101.32 ms | 402 KiB | 207 Q