- var_dump: documentation ( source)
- array_search: documentation ( source)
- array_slice: documentation ( source)
- array_keys: documentation ( source)
<?php
$array = array('foo' => 'a', 'bar' => 'b', 'baz' => 'c');
$insert_array = array('one' => 'two');
$key = 'bar';
$pos = array_search($key, array_keys($array)) ?: 0;
$array = array_slice($array, 0, $pos) + $insert_array + array_slice($array, $pos);
var_dump($array);