Table of Contents
PHP Arrays
Arrays are variables that can store multiple values in a single variable. PHP supports different types of arrays for various use cases.
Creating Arrays
Multiple ways to create arrays in PHP:
<?php
// Using array() function
$fruits = array("apple", "banana", "orange");
// Using short syntax (PHP 5.4+)
$colors = ["red", "green", "blue"];
// Empty array
$empty = [];
$empty2 = array();
// Mixed data types
$mixed = ["John", 25, true, 3.14];
?>Indexed Arrays
Arrays with numeric indexes (starting from 0):
<?php
$fruits = ["apple", "banana", "orange"];
// Accessing elements
echo $fruits[0]; // apple
echo $fruits[1]; // banana
echo $fruits[2]; // orange
// Adding elements
$fruits[3] = "grape";
$fruits[] = "kiwi"; // Automatically assigns next index
// Modifying elements
$fruits[0] = "pineapple";
print_r($fruits);
/*
Array
(
[0] => pineapple
[1] => banana
[2] => orange
[3] => grape
[4] => kiwi
)
*/
?>Associative Arrays
Arrays with named keys:
<?php
// Creating associative array
$person = [
"name" => "John Doe",
"age" => 30,
"city" => "New York",
"email" => "john@example.com"
];
// Accessing elements
echo $person["name"]; // John Doe
echo $person["age"]; // 30
// Adding/modifying elements
$person["phone"] = "123-456-7890";
$person["age"] = 31;
// Alternative syntax
$student = array(
"id" => 12345,
"name" => "Alice Smith",
"grade" => "A"
);
?>Multidimensional Arrays
Arrays containing other arrays:
<?php
// 2D array
$students = [
["John", 85, "Math"],
["Alice", 92, "Science"],
["Bob", 78, "History"]
];
// Accessing elements
echo $students[0][0]; // John
echo $students[1][1]; // 92
// Associative multidimensional array
$employees = [
"john" => [
"name" => "John Doe",
"position" => "Developer",
"salary" => 75000
],
"alice" => [
"name" => "Alice Smith",
"position" => "Designer",
"salary" => 65000
]
];
echo $employees["john"]["name"]; // John Doe
echo $employees["alice"]["salary"]; // 65000
?>Array Functions
Basic Array Functions
<?php
$numbers = [1, 2, 3, 4, 5];
// Count elements
echo count($numbers); // 5
echo sizeof($numbers); // 5 (alias of count)
// Check if array
var_dump(is_array($numbers)); // bool(true)
// Check if key exists
$person = ["name" => "John", "age" => 30];
var_dump(array_key_exists("name", $person)); // bool(true)
var_dump(isset($person["email"])); // bool(false)
// Check if value exists
var_dump(in_array("John", $person)); // bool(true)
var_dump(in_array(30, $person)); // bool(true)
?>Adding and Removing Elements
<?php
$fruits = ["apple", "banana"];
// Add to end
array_push($fruits, "orange", "grape");
$fruits[] = "kiwi"; // Alternative
// Add to beginning
array_unshift($fruits, "mango");
// Remove from end
$lastFruit = array_pop($fruits);
echo $lastFruit; // kiwi
// Remove from beginning
$firstFruit = array_shift($fruits);
echo $firstFruit; // mango
// Remove specific element
unset($fruits[1]); // Removes element at index 1
print_r($fruits);
?>Array Sorting
<?php
$numbers = [3, 1, 4, 1, 5, 9, 2, 6];
// Sort ascending
sort($numbers);
print_r($numbers); // [1, 1, 2, 3, 4, 5, 6, 9]
// Sort descending
rsort($numbers);
print_r($numbers); // [9, 6, 5, 4, 3, 2, 1, 1]
// Associative array sorting
$ages = ["John" => 30, "Alice" => 25, "Bob" => 35];
// Sort by value (keep keys)
asort($ages); // Alice=>25, John=>30, Bob=>35
// Sort by key
ksort($ages); // Alice=>25, Bob=>35, John=>30
// Reverse sorts
arsort($ages); // Sort by value descending
krsort($ages); // Sort by key descending
// Custom sorting
$students = [
["name" => "John", "grade" => 85],
["name" => "Alice", "grade" => 92],
["name" => "Bob", "grade" => 78]
];
usort($students, function($a, $b) {
return $b["grade"] - $a["grade"]; // Sort by grade descending
});
?>Array Manipulation
<?php
$numbers = [1, 2, 3, 4, 5];
// Array slice
$slice = array_slice($numbers, 1, 3); // [2, 3, 4]
// Array splice (remove and replace)
$removed = array_splice($numbers, 1, 2, ["a", "b"]);
// $numbers is now [1, "a", "b", 4, 5]
// $removed is [2, 3]
// Array merge
$array1 = [1, 2, 3];
$array2 = [4, 5, 6];
$merged = array_merge($array1, $array2); // [1, 2, 3, 4, 5, 6]
// Array combine (keys from one, values from another)
$keys = ["name", "age", "city"];
$values = ["John", 30, "NYC"];
$combined = array_combine($keys, $values);
// ["name" => "John", "age" => 30, "city" => "NYC"]
// Array flip (swap keys and values)
$original = ["a" => 1, "b" => 2, "c" => 3];
$flipped = array_flip($original); // [1 => "a", 2 => "b", 3 => "c"]
?>Array Filtering and Mapping
<?php
$numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
// Filter even numbers
$evens = array_filter($numbers, function($n) {
return $n % 2 == 0;
});
print_r($evens); // [2, 4, 6, 8, 10]
// Map - square each number
$squares = array_map(function($n) {
return $n * $n;
}, $numbers);
print_r($squares); // [1, 4, 9, 16, 25, 36, 49, 64, 81, 100]
// Reduce - sum all numbers
$sum = array_reduce($numbers, function($carry, $item) {
return $carry + $item;
}, 0);
echo $sum; // 55
// Array walk - modify array in place
array_walk($numbers, function(&$value, $key) {
$value = $value * 2;
});
print_r($numbers); // [2, 4, 6, 8, 10, 12, 14, 16, 18, 20]
?>Array Iteration
Different ways to loop through arrays:
<?php
$fruits = ["apple", "banana", "orange"];
// For loop (indexed arrays)
for ($i = 0; $i < count($fruits); $i++) {
echo $fruits[$i] . "
";
}
// Foreach loop
foreach ($fruits as $fruit) {
echo $fruit . "
";
}
// Foreach with index
foreach ($fruits as $index => $fruit) {
echo "$index: $fruit
";
}
// Associative array iteration
$person = ["name" => "John", "age" => 30, "city" => "NYC"];
foreach ($person as $key => $value) {
echo "$key: $value
";
}
?>Array Keys and Values
<?php
$person = ["name" => "John", "age" => 30, "city" => "NYC"];
// Get all keys
$keys = array_keys($person); // ["name", "age", "city"]
// Get all values
$values = array_values($person); // ["John", 30, "NYC"]
// Search for key by value
$key = array_search("John", $person); // "name"
// Get random key(s)
$randomKey = array_rand($person); // Random key
$randomKeys = array_rand($person, 2); // Array of 2 random keys
?>Practical Examples
Shopping Cart
<?php
class ShoppingCart {
private $items = [];
public function addItem($name, $price, $quantity = 1) {
if (isset($this->items[$name])) {
$this->items[$name]["quantity"] += $quantity;
} else {
$this->items[$name] = [
"price" => $price,
"quantity" => $quantity
];
}
}
public function removeItem($name) {
unset($this->items[$name]);
}
public function getTotal() {
$total = 0;
foreach ($this->items as $item) {
$total += $item["price"] * $item["quantity"];
}
return $total;
}
public function getItems() {
return $this->items;
}
}
$cart = new ShoppingCart();
$cart->addItem("Apple", 1.50, 3);
$cart->addItem("Banana", 0.75, 2);
echo "Total: $" . $cart->getTotal(); // Total: $6.00
?>Grade Calculator
<?php
function calculateGrades($students) {
$results = [];
foreach ($students as $name => $scores) {
$average = array_sum($scores) / count($scores);
$grade = getLetterGrade($average);
$results[$name] = [
"scores" => $scores,
"average" => round($average, 2),
"grade" => $grade
];
}
return $results;
}
function getLetterGrade($average) {
if ($average >= 90) return "A";
if ($average >= 80) return "B";
if ($average >= 70) return "C";
if ($average >= 60) return "D";
return "F";
}
$students = [
"John" => [85, 92, 78, 96],
"Alice" => [88, 91, 87, 93],
"Bob" => [72, 68, 75, 71]
];
$grades = calculateGrades($students);
print_r($grades);
?>Practice Exercise
Create a program that:
- Stores information about books (title, author, price, genre)
- Allows adding, removing, and searching books
- Calculates total value of all books
- Sorts books by different criteria
Key Takeaways
- Arrays can store multiple values in one variable
- Use indexed arrays for ordered data
- Use associative arrays for key-value pairs
- PHP provides many built-in array functions
- Choose the right array type for your data structure