PH PHP

PHP: Arrays

What you will learn

PHP arrays are ordered maps — they can serve as indexed arrays, associative arrays (key-value), or both at once.

Indexed arrays

$fruits = ["apple", "banana", "cherry"];
echo $fruits[0];       // apple
echo count($fruits);   // 3
$fruits[] = "date";    // adds to end

Short syntax with [] was introduced in PHP 5.4. Older code may use array("a", "b").

Associative arrays (key-value)

$user = [
    "name" => "Alice",
    "age" => 25,
    "active" => true
];
echo $user["name"];   // Alice
$user["role"] = "admin";  // add a new key

The => operator associates a key with a value.

Array operations

$numbers = [3, 1, 4, 1, 5];
sort($numbers);          // sort in place
array_push($numbers, 9); // add to end
$popped = array_pop($numbers); // remove from end
$reversed = array_reverse($numbers);
$exists = in_array(4, $numbers);   // true

The foreach loop

foreach ($fruits as $fruit) {
    echo $fruit;
}

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

Common mistakes

  • Using [] to access strings when you meant {} — $str[0] works but $str{0} is deprecated
  • Confusing array_push() with $arr[] = value — the latter is faster and more readable
  • Thinking PHP arrays are ordered by insertion (they are) — but sort() re-indexes numeric keys

Quick check below!

Next: Functions