Determine minimum and maximum of all CSV columns

Question

I need to find the minimum and maximum values of all the columns in CSV and use those values for my slider in my web page. Initially, I am determining the total columns in the CSV file and based on the total columns, I am creating those many sliders (like amazon's price slider). This is the piece of code for creating the sliders.

<?php
for ( $i = 1; $i < $totalcolumns; $i++ ) { 
    echo '<input type="text" data-slider="true" data-slider-range="1,500" data-slider-step="1"/>';
}
?> 

In the above piece of code, the data-slider-range is given as 1,500. However, I need to define these values based on the minimum and maximum values of my CSV columns. If I know my total columns beforehand, I am able to determine the minimum and maximum values of all the columns as discussed in this link.

Suppose if there are 5 columns in my CSV file, I need to include 5 sliders and find the minimum and maximum for all the 5 columns and use them as the data-slider-range in the above code.

Can someone please guide me in the right way? I am not sure if this is to be done in PHP or javascript as am entirely new to these technologies.

EDIT:

To find the total columns, I use another PHP file in which am using the below piece of code.

$handle = fopen('demo.csv', 'r');
if (($data = fgetcsv($handle, 1000, ',')) !== false) {
}

And then, I am using SESSION to pass the count($data) to my current PHP file.

$_SESSION["totalcolumns"] = count($data);

In my current PHP file, I am accessing the total columns in my CSV file as below.

$totalcolumns = $_SESSION["totalcolumns"];

Answer 1

You need to modify piece of code where you get $totalcolumns to:

$data = [];
$total_columns = 0;
$handle = fopen('data.csv', 'r');

while (false !== ($row = fgetcsv($handle, 1000, ','))) {
    0 === $total_columns and $total_columns = count($row);

    $i = 0;
    while (++$i <= $total_columns) {
        $data[$i][] = (int) $row[$i - 1];
    }
}

$i = 0;
while (++$i <= $total_columns) {
    $_SESSION["min-column-$i"] = min($data[$i]);
    $_SESSION["max-column-$i"] = max($data[$i]);
}

$_SESSION['totalcolumns'] = $total_columns;
fclose($handle);

For such data.csv:

3,4,5,6,7
10,8,1,8,8
3,6,7,8,2

you'll have this $_SESSION values:

var_dump($_SESSION);
array(11) {
    'min-column-1' => int(3)
    'max-column-1' => int(10)
    'min-column-2' => int(4)
    'max-column-2' => int(8)
    'min-column-3' => int(1)
    'max-column-3' => int(7)
    'min-column-4' => int(6)
    'max-column-4' => int(8)
    'min-column-5' => int(2)
    'max-column-5' => int(8)
    'totalcolumns' => int(5)
}

Then you'll be able to use range values like this:

$i = 0;
while (++$i <= $_SESSION['totalcolumns']) {
    $range = $_SESSION["min-column-$i"] . ',' . $_SESSION["max-column-$i"];
    echo '<input type="text"
                 data-slider="true"
                 data-slider-range="', $range, '"
                 data-slider-step="1"/>';
}