Why my php array is over written when they have same Keys - php

Question

I have a custom PHP function which executes a stored procedure and returns an array:
function test(){
$in = array("abc","bcd","efg");
$result = mydba->executestoredprocedure('proc1',$in);
$arr_sim = array();
foreach ($result['recordset'] as $rows) {
if (!empty($rows)) {
echo $arr_sim[$rows['field1']] = $rows['field2'];
}
}
return $arr_sim;
}
In the above function $arr_sim is returning the number of items correctly when the rows["field1"] values are different. If the rows["field1"] values are the same then it is overwriting the first value and returning only the last one. How can I overcome this?
array ( [chicago] => 'sears', [rochester] => 'liberty' )
If the $arr_sim contains these items then it is returned correctly. Because the keys are different.
array ( [chicago] => 'MCD', [chicago] => 'TACOBELL' )
If the $arr_sim contains these items then it is not returned correctly. Because the keys are the same, "chicago".

Answer 1

Array keys must be unique. Instead, do something like this:
// You want the array to look like this
// array('chicago' => array('MCD', 'TACOBELL'));
function test(){
$in = array("abc","bcd","efg");
$result = mydba->executestoredprocedure('proc1',$in);
$arr_sim=array();
foreach ($result['recordset'] as $rows) {
if(!empty($rows)){
if(array_key_exists($rows['field1'], $arr_sim) {
$arr_sim[$rows['field1']][] = $rows['field2'];
} else {
$arr_sim[$rows['field1']] = array($rows['field2']);
}
}
}
return $arr_sim;
}

Answer 2

Replace $arr_sim[$rows['field1']] = $rows['field2'] with $arr_sim[$rows['field1']][] = $rows['field2']. This will create an array of arrays.
echo $arr_sim['chicago'][0]; // MCD
echo $arr_sim['chicago'][1]; // TACOBELL
Technically, you should write something like this to avoid notices:
if (!isset($arr_sim[$rows['field1']])) $arr_sim[$rows['field1']] = array();
$arr_sim[$rows['field1']][] = $rows['field2'];
But you must really ask yourself, is the field1 (city names) worthy of being the primary key for the array? If not, you should choose some other identifier.