How can you group subarrays in PHP based on one column and create comma-separated values from another column within those groups?

Group Subarrays by One Column and Create Comma-Separated Values from Another Column within Groups

In PHP, grouping subarrays based on one column and concatenating values from another column within those groups poses a unique challenge. To tackle this problem, we provide a detailed solution that transforms a given array into a desired structured format.

The provided sample array consists of subarrays with two elements each. The goal is to group subarrays based on the second element (known as the "column") and create a new array where each element represents a group. Within each group element, the first element should be a comma-separated list of the first elements from the grouped subarrays, while the second element represents the common column.

To achieve this, we utilize a step-by-step approach:

1. Loop through the original array: Begin by iterating through each subarray in the original array.
2. Check for group key: For each subarray, check if the second element (group key) exists in a new array called $groups. If not, initialize an empty array for that group key.
3. Add subarray to group: Once the group key exists, add the first element of the current subarray to the corresponding group array.
4. Create the structured array: After processing the original array, loop through the $groups array. For each group, concatenate the values of its first elements using a comma and store them in a new array. Combine this with the group key to create the desired structure.

The provided PHP script below demonstrates this approach:

<code class="php">// Create the input array
$data = array(
    array('444', '0081'),
    array('449', '0081'),
    array('451', '0081'),
    array('455', '2100'),
    array('469', '2100')
);

// Initialize the groups array
$groups = array();

// Loop through the original array
foreach ($data as $item) {
    $key = $item[1];  // Get the group key

    // Check if the group key exists
    if (!array_key_exists($key, $groups)) {
        $groups[$key] = array();
    }

    // Add the subarray to the group
    $groups[$key][] = $item[0];
}

// Create the structured array
$structured = array();
foreach ($groups as $group => $values) {
    $structured[] = array(implode(',', $values), $group);
}

// Display the output
print_r($structured);</code>

This script effectively transforms the input array into a new array with the specified structure, where subarrays are grouped based on a common column, and the first elements of grouped subarrays are concatenated with commas.

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