- array_combine: documentation ( source)
- array_column: documentation ( source)
- print_r: documentation ( source)
- array_keys: documentation ( source)
<?php
$ar = [];
$ar['one'][] = 1;
$ar['one'][] = 2;
$ar['two'][] = 1;
$ar['two'][] = 2;
$ar['three'][] = 1;
$ar['three'][] = 2;
print_r($ar);
$keys = array_keys($ar);
$vals = array_column($ar,0);
$res = array_combine($keys,$vals);
print_r($res);