Splitting a list by the first letter

To categorize a list of items in PHP by their first letter, you can iterate through the list and group the items into a new associative array, where the keys are the first letters and the values ​​are arrays of items that begin with that letter.

Here is an example:

<?php 

$items = [
    "Apple",
    "Banana",
    "Cherry",
    "Date",
    "Apricot",
    "Blueberry",
    "Carrot",
    "Dragonfruit"
];

$groupedItems = [];

foreach ($items as $item) {
    $firstLetter = strtoupper(substr($item, 0, 1)); // Get the first letter and convert to uppercase
    
    // If the first letter key doesn't exist in $groupedItems, create an empty array for it
    if (!isset($groupedItems[$firstLetter])) {
        $groupedItems[$firstLetter] = [];
    }
    
    // Add the current item to the array corresponding to its first letter
    $groupedItems[$firstLetter][] = $item;
}

// Optional: Sort the grouped items by their first letter (key)
ksort($groupedItems); 

// Output the grouped items for demonstration
foreach ($groupedItems as $letter => $itemsInGroup) {
    echo "<h2>" . $letter . "</h2>";
    echo "<ul>";
    foreach ($itemsInGroup as $item) {
        echo "<li>" . $item . "</li>";
    }
    echo "</ul>";
} ?>

For Cyrillic text, replace substr() with mb_substr(). This is necessary for handling strings that use multibyte encodings. In Unicode, Russian characters take up 2 bytes, while Latin characters and spaces take up 1 byte.