Types of Arrays in PHP: Indexed, Associative, Multidimensional

Three shelves in one cupboard

1. Indexed array — numbered slots

<?php
$subjects = array("Hindi", "English", "Math");   // PHP 7.2 safe syntax
// $subjects = ["Hindi", "English", "Math"];      // short syntax, also fine

echo $subjects[0];          // Hindi  (counting starts at 0)
$subjects[] = "Science";    // append at the end

foreach ($subjects as $i => $sub) {
    echo ($i + 1) . ". " . $sub . "\n";
}
?>

2. Associative array — named slots (the DB-row shape)

<?php
$student = array(
    "roll_no" => 101,
    "name"    => "Aman",
    "class"   => "10",
    "fees"    => 1500.50
);

echo $student["name"];              // Aman - fetch by label

foreach ($student as $key => $value) {
    echo $key . " : " . $value . "\n";
}
?>

Look familiar? This is exactly what PDO's fetch(PDO::FETCH_ASSOC) returns for one database row, and what $_POST gives you from a form. Associative arrays are not a side topic — they ARE everyday PHP.

3. Multidimensional array — the full class register

<?php
$students = array(                            // array OF associative arrays
    array("roll" => 101, "name" => "Aman",  "marks" => 92),
    array("roll" => 102, "name" => "Priya", "marks" => 88),
    array("roll" => 103, "name" => "Rahul", "marks" => 76)
);

echo $students[1]["name"];       // Priya  (row 1, column "name")

// The pattern you will write 1000 times (fetchAll gives this exact shape):
foreach ($students as $s) {
    echo $s["roll"] . " - " . $s["name"] . " - " . $s["marks"] . "\n";
}
?>

The helper functions you will actually use

<?php
$marks = array(92, 88, 76);

echo count($marks);              // 3       - how many elements
echo array_sum($marks);          // 256     - total
echo max($marks);                // 92      - topper
sort($marks);                    // ascending: 76, 88, 92
print_r($marks);                 // debug view of any array
echo in_array(88, $marks) ? "yes" : "no";   // yes - value exists?
echo implode(", ", $marks);      // "76, 88, 92" - array -> string
$parts = explode(",", "a,b,c");  // string -> array
?>

Interview line: "PHP arrays are ordered maps wearing three shapes — indexed for lists, associative for records, multidimensional for tables — and foreach with $key => $value handles them all."