SQL query fails in php function

Question

function getDeviceTableCount($fieldnameIn) {
$sqlDeviceCount = "SELECT COUNT(" . $fieldnameIn . ") as total FROM `devices`";
$countDeviceTone = mysqli_query($conn, $sqlDeviceCount);
$data=mysqli_fetch_assoc($countDeviceTone);
$totalQ = $data['total'];
return $totalQ;
}

Hey everyone, Thanks for taking the time to read my problem. I am making a function to return the count of a column in a MYSQL Database. Unfortunately, this function does not return the total number of items in the column.

I know the query works. I was wondering if the problem is putting a php variable in an sql string because I need the user to be able to change the table the app queries from.

If anyone can shed some light on why this doesn't work, I'd appreciate it.

The problem is not putting a php variable in the SQL string - that's perfectly fine. Where is the $conn variable being set? Are you sure it's not "null"? — jackel414
– jackel414, Commented Jun 3, 2015 at 17:03
Make sure $fieldnameIn value is not a default MySQL keyword if it is the case add ` around your field name. — jaym
– jaym, Commented Jun 3, 2015 at 17:04
Does it return a count at all? Does that count happen to exclude NULL values? What does Select count(*) from devices vs Select count(Fieldname) from devices vs select count(1) from devices where fieldName is null each return? — xQbert
– xQbert, Commented Jun 3, 2015 at 17:08

donald123 · Accepted Answer · 2015-06-03 17:04:59Z

1

in your funtion $conn is unkonwn :(

so if you prefer such a handling, give your DBDMS connection to your function

function getDeviceTableCount($fieldnameIn, $conn) {
....
}

or use global in your function (that is what you not will ,)

or build a new connection inside your function (that is what you also not will)

answered Jun 3, 2015 at 17:04

donald123

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fsacer · Accepted Answer · 2015-06-03 17:09:15Z

1

There multiple problems here. One is almost certainly the $conn. The other problem here might be the SQL injectipn which might be easily resolved with mysqli_real_escape_string() function. If you want the user to specify the table pass it as parameter also and escape it.

answered Jun 3, 2015 at 17:09

fsacer

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