<?php

$x = [ 'id_ext' => [ 'NULLOP' => [ 'EQ' => [ '1234' ] ] ] ];
var_dump($x);
foreach ($x as $k1 => $v1) {
    $attr = $k1;
    foreach ($v1 as $k2 => $v2) {
        foreach ($v2 as $k3 => $v3) {
            // k3 should be op-eq
            echo 'count(v3) = ' . count($v3) . PHP_EOL;
            $value = $v3[0];
        }
    }
}
echo "Attribute: $attr, Value: $value" . PHP_EOL;