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<?php $array1 = [ '1' => '11', 'b' => 1, 3 => 33, 8 => 8 ]; $array2 = [ '1' => '22', 'b' => 2, 3 => 44, 9 => 9 ]; foreach ($array2 as $key => $value) { if (!key_exists($key, $array1)) { $array1[$key] = $value; } else { $array1[$key] = (array)$array1[$key]; $array1[$key][] = $value; } } var_export($array1);
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 - 8.3.27, 8.4.1 - 8.4.14
array ( 1 => array ( 0 => '11', 1 => '22', ), 'b' => array ( 0 => 1, 1 => 2, ), 3 => array ( 0 => 33, 1 => 44, ), 8 => 8, 9 => 9, )
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 ( 1 => array ( 0 => '11', 1 => '22', ), 'b' => array ( 0 => 1, 1 => 2, ), 3 => array ( 0 => 33, 1 => 44, ), 8 => 8, 9 => 9, )

preferences:
184.84 ms | 408 KiB | 5 Q