Max value of an array in PHP

Question

Why isn't this working? Is there something wrong with my syntax or anything? I want to echo the max value of the $row2['startShift'] array but it displays nothing.

$query2 = "SELECT startShift,endShift from seats where seatid=".$row['seatid'];
$result2 = mysql_query($query2);
while ($row2 = mysql_fetch_array($result2)){
 $startShift = $row2['startShift'];
 echo max($startShift);
}

• Faytraneozter: you want to count all value?
• rez: No i just want to display the maximum value so I used max() but it doesn't echo anything. Any ideas why and how?
• user557846: becuse its inside the loop, and you could just get it from the db rather thing get all rows for this one value
• Jorg: $row is a single row, so $row['startShift'] is not an array. Why not stick max in the query?
• erik258: Why not have MySQL handle your data for you, rather than pulling back results you don't want? SELECT MAX(startShift) FROM seats WHERE seitid = @seat_id" ?

Answer 1

You calculate a maximum by keeping a separate variable outside of the loop:

$maxStartShift = -INF;
while ($row2 = mysql_fetch_array($result2)){
 if ($row2['startShift'] > $maxStartShift) {
 $maxStartShift = $row2['startShift'];
 }
 echo $maxStartShift; // maximum until now
}

The max() function returns the maximum value of it's arguments, so max(1, 2) == 2 or max([1, 2]) == 2. In your case:

echo max($row2['startShift']);

Will just return $row2['startShift'] because that's the maximum of all arguments passed to the function.

• rez: Im sorry im just a beginner in PHP but can i ask one stupid question? What is $maxStartShift = -INF? and what it's for?
• Jorg: INF is a php constant representing "infinity". If you don't give $maxStartShift a very low initial value, the greater-than comparison might not work.
• rez: I have one more favor to ask. If want the minimum value now, how should I go on about this?
• Ja͢ck: @rez You do the same thing but in reverse; you start with a value of INF and then compare if anything is lower than the current minimum.