row length, for loop

lukeurtnowski

I have a table with many fields (m1, m2, m3, m4, up to m29). I have many rows of data and some of the rows stop at m5, and others at m21, and others stop at m17). I was wondering if there is some sort of for loop that would help me to determint the lingth of these rows.

olaf

why you want to know this?

lukeurtnowski

Well, I'm trying to constrict a combo box to cut oput all the blank space, to see it, go www.lukesplace.com/jeff and follow the 3 steps (combo boxes) and you'll see.

olaf

ok i understand:

then you have to use a loop for all fields and check the box if not empty...

lukeurtnowski

should I do something like this?

for(x=0; x==Make.length; x+1)
{
printf('<option value="'.$result1['mx'] . '">'.$result1['m1'] . '</option>');
}

olaf

Yes, and add an if statement for the checked value ...

lukeurtnowski

why do I add an if statement? Won't the for loop take care of it

tsinka

Hi,

does a row always contain data in m1 to m? or is it possible that it contains data in e.g. m1,m5 and m6 ? What is the default value of the fields in the table ... null or an empty string ?

Examples:

containing data in m1....m?
```
$sql = "SELECT * FROM thetable";
$res = mysql_query($sql) or die ("SQL error: ".mysql_error());

while ($row = mysql_fetch_array($res) && !$finished) {
  $finished = false;
  foreach ($row as $key => $value) {
    if (strlen($value)) {
      // print option stuff
    } else {
      $finished = true;
    }
  }
}
```
1. containing data in any way:
Use the same code as above but just without the $finished stuff.

Another way could be to use the php function array filter http://de3.php.net/manual/en/function.array-filter.php to remove the empty values from the array. Use a callback function that checks if the given element is empty. After that you'll have an array that just contains valid data and with a count($array) you can get the number of elements in that array.

One question:

What's the reason for that table layout ? Which data is stored in the table.

Thomas

lukeurtnowski

Istore makes of each model of car

tsinka

Hi,

a solution with two tables might be better because the fields not used are a waste of space. Additionally, you wouldn't have to use code like the one above.

Thomas

lukeurtnowski

I have a question, In the code you gave me I'm a little vague on how to make the option dependent on the length of that tables row (heres the code)
$sql = "SELECT * FROM thetable";
$res = mysql_query($sql) or die ("SQL error: ".mysql_error());

while ($row = mysql_fetch_array($res) && !$finished) {
$finished = false;
foreach ($row as $key => $value) {
if (strlen($value)) {
// print option stuff
} else {
$finished = $finished = true;
}
}
}

I'm a little confused on the commented part(//print option stuff here). I know how to do it once(printf('<option value="'.$result1['mx'] . '">'.$result1['m1'] . '</option>'); ) but what should I used so a different field is selected each time the loop is run?

thanks a lot thomas

tsinka

Hi,

just replace

// print the option stuff

echo "<option value=\"$key\">$value</option>";

Do you have a unique id besides the m??? fields in that table ?

You would need one to use for the select name to identify the row that was used to create the drop down list.

If someone submits the form you would get a post variable like

$_POST['nameofselect'] containing the field that was selected, like e.g. m1

Thomas

Roger_Ramjet

Hi,

tsinka is right when he suggests reorgansing your table structure as the solution.

Instead of putting all models on one row, and ending up with a lot of empty fields, just break each model out into it's own row with make and year fields. This will make far more flexible queries and result sets possible, result sets without empty fields to code for. Visitors could then eg. enter the name of their model and be presented with a list of years to select from, as well as following your chain of combo boxes.

Just a thought.

lukeurtnowski

Your solutioon is better, Sorry for taking so long to reply (I tried to figure this out). Can you explain your solutioon to me like your talking to a newbie, thanks a lot.