Question

So I have two arrays, $gDatabaseKeyNames (list of column names) and $gDatabaseKeyValues (a list of variable names containing values from a script). The variable names are generated dynamically so I keep track of them for an insert.

Rather than listing all of the columns and value variables, I tried this

$cols = implode(", ", array_values($gDatabaseKeyNames));
$vals = implode(", ", array_values($gDatabaseKeyValues));

$query = "INSERT INTO pings (survey_id, $cols) VALUES ('$surveyID', $vals)";                              
mysql_query ($query) or die(mysql_error());

But none of my actual values show up in the database (they are inserted as 0s – all my columns are numeric).

If I echo $query, I see this, which is the correct formatting:

INSERT INTO pings (survey_id, latitude, longitude, pingTimestamp) VALUES ('15', '$Dlatitude', '$Dlongitude', FROM_UNIXTIME('$DtimeStamp'))

However, if I change $query to

$query = INSERT INTO pings (survey_id, latitude, longitude, pingTimestamp) VALUES ('$surveyID', '$Dlatitude', '$Dlongitude', FROM_UNIXTIME('$DtimeStamp'));

It works perfectly!

Why isn’t PHP interpreting the variables in the implode? How can I fix this?

Answer 1

I suspect that $cols has the literal value '$Dlatitude', '$Dlongitude', etc.... PHP does not “double-interpolate” strings. It’ll replace $cols with its values, but will NOT replace $Dlatitude with that variable’s value. In other words, you’re literally inserting some strings-that-look-like-PHP-variable-names into your numeric fields.

What is in the $gDatabaseKeyValues/Names arrays?