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Using Arrays and Functions in PHP (Easy Guide)

In PHP, arrays store multiple values in a single variable, and functions group reusable code. Together, they make your programs cleaner, faster, and easier to maintain. This guide explains how to create and use arrays, loop through them, and write functions that work with arrays.

Types of Arrays in PHP

• Indexed array: Values accessed by numeric index (0, 1, 2, ...).
• Associative array: Values accessed by named keys.
• Multidimensional array: Arrays inside arrays (useful for tables or records).

Create and Access Arrays

 21,
    "Ravi" => 20
];
echo $ages["Asha"]; // 21

// Check key safely
$rahulAge = $ages["Rahul"] ?? "not found";

// Multidimensional array
$students = [
    ["name" => "Asha", "marks" => 86],
    ["name" => "Ravi", "marks" => 74]
];
echo $students[1]["name"]; // Ravi
?>

Loop Through Arrays

 "India", "US" => "United States"];
foreach ($countryCodes as $code => $country) {
    echo "$code => $country\n";
}
?>

Common and Useful Array Functions

• count: Number of elements.
• array_push / array_pop: Add/remove from end.
• array_merge: Combine arrays.
• in_array / array_search: Find values.
• sort / rsort: Sort by values (indexed arrays).
• asort / ksort: Sort associative arrays (by value/key).
• array_slice / array_splice: Extract or modify parts of arrays.
• array_map / array_filter / array_reduce: Functional operations.

 2, "a" => 3, "c" => 1];
asort($assoc); // sort by value: c=>1, b=>2, a=>3
ksort($assoc); // sort by key: a=>3, b=>2, c=>1

// Map, filter, reduce
$squared = array_map(fn($x) => $x * $x, [1,2,3]);      // [1,4,9]
$evens   = array_filter([1,2,3,4], fn($x) => $x % 2==0); // [2,4]
$sum     = array_reduce([1,2,3], fn($carry,$x)=>$carry+$x, 0); // 6
?>

Defining and Calling Functions

Functions help you reuse logic. You can set default values, declare parameter types, and specify return types for safety.

Working with Arrays in Functions

Multidimensional Arrays with Functions (Mini Example)

 "Asha", "marks" => [80, 90, 85]],
    ["name" => "Ravi", "marks" => [70, 60, 75]],
    ["name" => "Neha", "marks" => [88, 92, 91]]
];

function studentAverage(array $marks): float {
    return average($marks); // reusing the earlier average() function
}

function topStudent(array $students): array {
    $best = ["name" => "", "avg" => -1.0];
    foreach ($students as $s) {
        $avg = studentAverage($s["marks"]);
        if ($avg > $best["avg"]) {
            $best = ["name" => $s["name"], "avg" => $avg];
        }
    }
    return $best;
}

foreach ($students as $s) {
    echo $s["name"] . " avg: " . studentAverage($s["marks"]) . "\n";
}

$top = topStudent($students);
echo "Topper: {$top['name']} with {$top['avg']}\n";
?>

Best Practices and Tips

• Use descriptive keys in associative arrays for readability.
• Check keys with isset or array_key_exists before accessing.
• Use type hints (array, int, string) and return types for safer code.
• Prefer foreach for array traversal; it’s simple and clear.
• Use built-in array functions to avoid writing manual loops for common tasks.

Quick Checklist for Exams

1. Know how to declare indexed, associative, and multidimensional arrays.
2. Access, insert, update, and delete elements.
3. Use foreach to iterate over arrays.
4. Apply key array functions: count, sort, in_array, array_merge, array_map/filter/reduce.
5. Define functions with parameters, defaults, and return values.
6. Pass arrays to functions and return arrays from functions.
7. Understand type declarations and passing by reference when needed.