<?php
$numbers    = array(
    10,
    20,
    100,
    30,
    40,
    104,
    200,
    202,
    33
);
$bestValue1 = $numbers[0];
$bsetValue2 = $numbers[1];
$lastDif    = abs($numbers[0] - $numbers[1]);
 
for ($i = 1; $i < count($numbers); $i++) {
 
    for ($k = 0; $k < $i; $k++) {
 
        $dif = abs($numbers[$k] - $numbers[$i]);
 
        if ($dif == 0) {
            continue;
        }
        if ($dif < $lastDif) {
            $lastDif    = $dif;
            $bestValue2 = $numbers[$k];
            $bestValue1 = $numbers[$i];
        }
    }
 
}
$pair = array(
    $bestValue1,
    $bestValue2
);
print_r($pair);
 
?>

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