<?php
$array = [0 => ["number", null, "274", null, null, null, null, null, null, null],
1 => ["step", null, "4", null, null, null, null, null, null, null],
19 => ["details", null, null, null, null, null, null, null, null, null]];
$new_array = array_combine(array_column
($array, 0), array_column
($array, 2));
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