Max Values in Array of Arrays

[PHPBewildered]

I want to identify the highest number for each place in an array of arrays. I think that the max function (http://www.php.net/manual/en/function.max.php) must be the one to use but I am having trouble getting it to work properly.

Here is the code for what I am trying to do. The data is being graphed on line charts and I want to determine the maximum values for scaling purposes.

// create query
$sql = "SELECT second, val1, val2, val3, val4, val5 FROM valtable WHERE (date_time = '$qdatetime' AND test_id = '$testid') ORDER BY second ASC";

$queryvals = odbc_exec($connectionstring, $sql);

// create two arrays of arrays with the data (each line item is an array of one second's worth of data)
$adata = array();
$bdata = array();
while($row = odbc_fetch_row($queryvals))
{
$sec = odbc_result($queryvals, "second");
$val1 = odbc_result($queryvals, "val1");
$val2 = odbc_result($queryvals, "val2");
$val3 = odbc_result($queryvals, "val3");
$val4 = odbc_result($queryvals, "val4");
$val5 = odbc_result($queryvals, "val5");
$apersecdata = array($sec, $val1, $val2, $val3);
array_push($adata,$apersecdata);
$bpersecdata = array($sec, $val4, $val5);
array_push($bdata,$bpersecdata);
}

// count arrays in each array
$howmanya = count ($adata);
$howmanyb = count ($bdata);

// determine maximum values
$maxval5 = max($bdata[$val5],0);
$maxval4 = max($bdata[$val4],0);
$maxval3 = max($adata[$val3],0);
$maxval2 = max($adata[$val2],0);
$maxval1 = max($adata[$val1],0);
$maxsec = max($adata[$sec],0);

The last section (determine maximum values) doesn't work right. Can anyone give me some guidance on how to find out the maximum values of each element in the array of arrays?

[nemonoman]

I'm looking at this statement:

$maxval5 = max($bdata[$val5],0);

I'm not sure that $bdata[$val5] exists--
I think you mean to reference
$bdata[2],

which is where you stored $val5

But as written, I don't think $bdata[$val5] has that meaning.

$maxval5 = max($bdata[2],0);

should return the value you expect.

[nemonoman]

anyway, the simpler answer would be to capture the max value earlier:

$val1 = odbc_result($queryvals, "val1");
$maxval=max($val1,0);

easier to understand and maintain, IMO.

[PHPBewildered]

Thanks for the assistance. I tried the first suggestion:

$maxval5 = max($bdata[2],0);

and it did return a value but not the one I expect. It returns the max value in the third [2] sub-array rather than the highest third place value out of all of the sub-arrays.

Then I tried the second suggestion (capture the max value earlier):

$val1 = odbc_result($queryvals, "val1");
$maxval=max($val1,0);

This didn't work either. It returned the values in the last sub-array. I think that this is because the statement is in the "while($row = odbc_fetch_row($queryvals))" loop, so the $maxval is updated for each sub-array in the array. So, at the end of the loop, after all sub-arrays have been looped through, the $maxval is left as the value in the last sub-array.

What I ended up trying was adding if statements to the loop so that $maxval would only be updated if the value in the current sub-array is higher:

$val1 = odbc_result($queryvals, "val1");
if($maxval1 < $val1)
{
$maxval1=$val1;
}

It works but is it the most efficient way?

[nemonoman]

try:

$maxval=max($val1,$maxval);

You may need to initialize $maxval=0 before you start the loop.

[PHPBewildered]

That works also and is obviously more efficient. Thanks a bunch!