php: looping thru results from mysql query to increment counter (associative array) - php

Question

I'm retrieving data from a MySQL db and creating reports from it. I need to get counts when certain conditions are met, and since db queries are rather expensive (and I will have a lot of traffic), I'm looping thru the results from a single query in order to increment a counter.
It seems like it's working (the counter is incrementing) and the results are somewhat close, but the counters are not correct.
At the moment, there are 411 records in the table, but I'm getting numbers like 934 from a ['total'] counter and 927 for ['males'], and that definitely can't be right. However, I get 4 from ['females'], which is correct…
I'm pretty sure it was working last night, but now it's not—I'm quite baffled. (there are still just 411 records)
$surveydata = mysql_query("SELECT `age`,`e_part`,`gender` FROM $db_surveydata;") or die(mysql_error());
$rowcount = mysql_num_rows($surveydata);
$age=array('18+'=>0,'<18'=>0,'total'=>0);
$e_part=array('yes'=>0,'no'=>0,'total'=>0);
$genders=array('male'=>0,'female'=>0,'trans'=>0,'don\'t know'=>0,'total'=>0);
while ($responses = mysql_fetch_assoc($surveydata)) {
foreach ($responses as $response){
switch ($response){
case $responses['age']:
if ($responses['age'] > 18) {$age['18+']++;$age['total']++;}
// i tried putting the ['total'] incrementer in the if/else
// just in case, but same result
else {$age['<18']++;$age['total']++;}
break;
case $responses['e_part']:
if ($responses['e_part']) {$e_part['yes']++;}
else {$e_part['no']++;}
$e_part['total']++;
break;
case $responses['gender']:
switch ($responses['gender']){
case 1:$genders['male']++;break;
case 2:$genders['female']++;break;
case 3:$genders['trans']++;break;
case 9:$genders['don\'t know']++;break;
default:break;
}
$genders['total']++;
break;
default:break;
} // end switch
} //end for
} // end while
thanks!

Answer 1

this is the problem:
foreach ($responses as $response){
switch ($response){
case $responses['age']:
switch $responses looks for match
foreach ($responses as $k=>$v){
switch ($k){
case 'age':
if ($v > 18) ....

Answer 2

mysql_fetch_assoc() retrieves a single row from the table. You then loop over that row, processing each individual field. Then the long set of if() checks to determine which field you're on. That entire structure could be changed to:
while($response = mysql_fetch_assoc($surveydata)) {
if ($responses['age'] > 18) {
$age['18+']++;
} else {
$age['<18']++;
$age['total']++;}
if ($responses['e_part']) {
$e_part['yes']++;
} else {
$e_part['no']++;
}
$e_part['total']++;
switch ($responses['gender']){
case 1:$genders['male']++;break;
case 2:$genders['female']++;break;
case 3:$genders['trans']++;break;
case 9:$genders['don\'t know']++;break;
default:break;
}
$genders['total']++;
}

Answer 3

There's no need for the switch ($response); you can't really switch on an array like that. And even if you could, the 'values' you get wouldn't make any sense -- i'm thinking if it works at all, the value you're switching on would be either 'Array' or the length of the array. (I forget how PHP handles arrays-as-scalars.)
You'll want something like this...
$total = 0;
while ($response = mysql_fetch_assoc($surveydata))
{
if (isset($response['age']))
{
++$age[($response['age'] < 18) ? '<18' : '18+'];
++$age['total'];
}
if (isset($response['e_part']))
{
++$e_part[($responses['e_part']) ? 'yes' : 'no'];
++$e_part['total'];
}
if (isset($response['gender']))
{
switch ($response['gender'])
{
case 1: ++$genders['male']; break;
case 2: ++$genders['female']; break;
case 3: ++$genders['trans']; break;
case 9: ++$genders["don't know"]; break;
}
++$genders['total'];
}
++$total;
}
The benefit of the if (isset(...)) is that if 'age', 'e_part', or 'gender' is null, the corresponding code to count it won't get activated. It does about the same thing as your code, minus the embarrassing loop -- and minus the counting of the field even though it is null, because every row will have the same fields.