[php] "Notice: Undefined variable", "Notice: Undefined index", and "Notice: Undefined offset" using PHP

Another reason why an undefined index notice will be thrown, would be that a column was omitted from a database query.

I.e.:

$query = "SELECT col1 FROM table WHERE col_x = ?";

Then trying to access more columns/rows inside a loop.

I.e.:

print_r($row['col1']);
print_r($row['col2']); // undefined index thrown

or in a while loop:

while( $row = fetching_function($query) ) {

    echo $row['col1'];
    echo "<br>";
    echo $row['col2']; // undefined index thrown
    echo "<br>";
    echo $row['col3']; // undefined index thrown

}

Something else that needs to be noted is that on a *NIX OS and Mac OS X, things are case-sensitive.

Consult the followning Q&A's on Stack:

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