CodeIgniter 3 MySQL query randomly works intermittently - php

Question

I made a function in a CI model that first queries for the table to get its fields(because these fields will change dynamically over time,so I can't hard code a list of field names),and then when it gets the results of the first query, and builds a fields name list,it queries the table again to get the values belonging to one row or record.It then stores the second query result in an array,which is passed back to the controller.Here is the complete function that performs these steps:
public function getAssetFeatures($as_id)
{
$data = array();
//this sql query gets the field names from the table I want to query.
$sql = "SELECT COLUMN_NAME FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_SCHEMA = '".DATABASE."' AND TABLE_NAME = 'as_features';";
$query = $this->db->query($sql);
$count = 0;
foreach($query->result_array() as $k)
{
foreach($k as $kk=>$v)
{
if( $v != "as_features_id" &&
$v != "as_id" &&
$v != "cid" &&
$v != "lot_size" )
{
$features_array[$count] = $v;
$count++;
}
}
}
$features_string = implode(",",$features_array);
//I got the field names, put them into an array, then concatenated them into a string, which I will use for the fields in the next query:
$sql = "SELECT $features_string FROM as_features WHERE as_id='$as_id'";
$query = $this->db->query($sql);
//mandatory rooms/features:
foreach($query->result() as $row)
{
foreach($row as $k=>$v)
{
$data["$k"] = $v; //build an associative array with the values of each field for the one row I am querying
}
}
return $data; // return the associative array.
}
At first I thought something was broken in my table or view,but as I kept repeating the same call to the model function by refreshing the page and entering the exact same values,I noticed that sometimes the code worked,and I wouldn't get the errors "undefined index".
So I outputted the results of the array with this code:
echo "<pre>";
print_r($asset['features']);
echo "</pre>";
...and the expected output, which only performs successfully sometimes, but not all the time, for the exact same operation using the exact same parameters, looks like this:
Array
(
[kitchen] => 1
[liv_area] => 0
[dining] => 1
[family] => 0
[bed] => 0
[bath] => 1
[half_bath] => 0
[parking] => 0
[car_storage] => 0
[pool] => 0
[miscellaneous] => 0
)
When the query returns a result set and then a populated array,my form works and looks normal.but,most of the time the query fails,and I get what looks like this:

Answer 1

The issue is with the following snippet of code:
foreach($query->result() as $row)
{
foreach($row as $k=>$v)
{
$data["$k"] = $v; //build an associative array with the values of each field for the one row I am querying
}
}
The way it works is that for every result which is returned it will overwrite $data with the relevant keys. However, because the $query->result() will return the row you want, then return false, the array essentially ends up being:
$data[] = false; i.e., set the whole array to false/empty.
If you change the loop to be, the code inside the loop won't be executed for the false value of $query->result():
while ($row = $query->result())
{
// your code
}
It's worth noting that if you're intending to return more that one row from this, it won't work as it will just overwrite the existing values.

Answer 2

Ok, the problem was my code, not the query. I was passing an encrypted as_id, but neglected to unencrypt it before constructing the select query. That's why it would work sometimes, and not others. For some reason MySQL allowed the encrypted as_id to match existing as_id of INT type. After performing the decrypt, the query results became predictable. This is something I wouldn't expect SO members to have divined. Thanks.
public function getAssetFeatures($as_id)
{
$as_id = $this->utilityclass->decryption9($as_id); // <- I had this commented out. In fact, I removed the line from my example code in the original post, because I didn't think it was important to the question. Not only was it important, it was the problem!
$data = array();
$sql = "SELECT COLUMN_NAME FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_SCHEMA = '".DATABASE."' AND TABLE_NAME = 'as_features';";
$query = $this->db->query($sql);