与mysqli_fetch_array混淆

Question

I am unfamiliar with the mysqli_fetch_array and can't seem to figure this out. I have the following code:

function select_fetch_row ($arg1, $arg2) {
    $con = new mysqli(/* ... */);
    $query = "SELECT $arg1 FROM $arg2";
    $select = mysqli_query($con, $query);
    while($row = mysqli_fetch_array($select, MYSQLI_NUM)){
        echo $row[0];
    }

}

select_fetch_row(/* parameters*/);

However I'm not understanding what it's supposed to be doing. I was expecting to obtain an array where each key would correspond to a row in my table, but when I output my code, rather than just having the value of the first row ( $row[0] ) echoed, all the values of the column get echoed. Can someone shed some light on how this function really works?

Answer 1

while($row = mysqli_fetch_array($select, MYSQLI_NUM)){
        echo $row[0];
    }

You're fetching the rows one by one, not in a single array. So each $row variable has a single row from your table, with each key containing a column value. So when you echo $row[0], you're showing the first column of the row you've returned.

If you change the parameter MYSQLI_NUM to MYSQLI_ASSOC, you'll have a better idea of what's happening (the array keys will contain the column names instead of integers).

If you want to fetch all the rows in one go, you can use mysqli_fetch_all instead, which will give you one big array, containing one row per key.

http://www.php.net/manual/en/mysqli-result.fetch-array.php

http://www.php.net/manual/en/mysqli-result.fetch-all.php