Online PHP editor | output for GWoNH

@ 2022-01-23T12:58:14Z

<?php

$first = [
    'c' => 'd',
    'm' => 'n',
];

$second = [
    'C' => 'd',  // first encounter, qualifying key, qualifying value (['c' => 'd'] is removed from result)
    'c' => 'D',  // doesn't matter
    'm' => 'N',  // first encounter, qualifying key, disqualifying value
    'M' => 'n',  // this should eliminate ['m' => 'n'], but doesn't get the chance
];

/* behavior discovered while crafting this answer: 
 * https://stackoverflow.com/a/70817582/2943403
 */

var_export(
    array_diff_uassoc(
        $first,
        $second,
        'strcasecmp'
    )
); // removes first-occurring, case-insensitive key, case-sensitive value

Output for 7.0.0 - 7.0.33, 7.1.0 - 7.1.33, 7.2.0 - 7.2.34, 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 - 8.2.18, 8.3.0 - 8.3.6: array ( 'm' => 'n', )
Output for 5.4.0 - 5.4.45, 5.5.0 - 5.5.38, 5.6.0 - 5.6.40: array ( )
Output for 4.4.2 - 4.4.9, 5.1.0 - 5.1.6, 5.2.0 - 5.2.17, 5.3.0 - 5.3.29: Parse error: syntax error, unexpected '[' in /in/GWoNH on line 3
Process exited with code 255.
Output for 4.3.0 - 4.3.1, 4.3.5 - 4.3.11, 4.4.0 - 4.4.1, 5.0.0 - 5.0.5: Parse error: parse error, unexpected '[' in /in/GWoNH on line 3
Process exited with code 255.
Output for 4.3.2 - 4.3.4: Parse error: parse error in /in/GWoNH on line 3
Process exited with code 255.

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