попробуйте как следует
<?php
$var = array(
array(
'tih_sku' => '10001',
'tih_style' => 'RHH/110/02',
'tih_color' => 'BLACK',
'tih_leather' => 'PERU',
'bom_dt' => array(
array(
'mm_spec_fld' => 'NO 5, 44.5 CM - METAL - BLACK',
'tbid_qnty' => '1',
'mi_sku' => 'RHH/110/04 BLACK',
),
array(
'mm_spec_fld' => 'NO 3 - NYLON',
'tbid_qnty' => '7.75',
'mi_sku' => 'RHH/110/04 BLACK',
)
),
),
array(
'tih_sku' => '10009',
'tih_style' => 'RHH/110/04',
'tih_color' => 'BLACK',
'tih_leather' => 'PERU',
'bom_dt' => array(
array(
'mm_spec_fld' => 'NO 5, 68 CM - METAL - BLACK',
'tbid_qnty' => '1',
'mi_sku' => 'RHN/208/02 BLACK',
),
array(
'mm_spec_fld' => 'NO 5',
'tbid_qnty' => '17',
'mi_sku' => 'RHN/208/02 BLACK',
)
),
)
);
?>
<?php if(array_filter($var)){ ?>
<style>
table{width:50%;}
td{border:1px solid #999;padding:5px;}
</style>
<table>
<tr><td>Specification</td><td>Quantity</td><td>Code</td></tr>
<?php
$returnArray = array_map(function($v){ return $v['bom_dt'];},$var);
array_walk($returnArray, function($v2){array_walk($v2, function($v3){
?>
<tr><td><?=$v3['mm_spec_fld'];?></td><td><?=$v3['tbid_qnty'];?></td><td><?=$v3['mi_sku'];?></td></tr>
<?php
});});
?>
</table>
<?php } ?>
демо: https://paiza.io/projects/bhrSiwQi5zxtSMAz7ev0Wg?language=php