- var_dump: documentation ( source)
- array_merge: documentation ( source)
<?php
$yaml = ['suites' => ['asdfadf'> 3], 'extensions' => ['abd' => [''], 'bbb' => null]];
$extensions = ['newExt' => ['bbaba' => 111]];
var_dump(array_merge($yaml, ['extensions' => $entensions]));