PHP Array Functions

PHP includes a large library of built-in array functions that handle common operations — sorting, searching, merging, filtering, and transforming arrays. Using these functions avoids writing repetitive loops and keeps code clean and readable.

Sorting Arrays

sort() — Sort Indexed Array Ascending

<?php
  $prices = [49.99, 12.50, 89.00, 7.25, 34.00];
  sort($prices);

  print_r($prices);
  // Array ( [0] => 7.25 [1] => 12.5 [2] => 34 [3] => 49.99 [4] => 89 )
?>

rsort() — Sort Indexed Array Descending

<?php
  $numbers = [3, 1, 4, 1, 5, 9, 2, 6];
  rsort($numbers);

  echo $numbers[0];   // Outputs: 9  (highest first)
?>

asort() — Sort Associative Array by Value (Preserve Keys)

<?php
  $scores = ["Alice" => 88, "Bob" => 72, "Carol" => 95, "Dave" => 81];
  asort($scores);

  foreach ($scores as $name => $score) {
    echo $name . ": " . $score . "<br>";
  }

  // Outputs (sorted by score):
  // Bob: 72
  // Dave: 81
  // Alice: 88
  // Carol: 95
?>

ksort() — Sort Associative Array by Key

<?php
  $inventory = ["banana" => 30, "apple" => 50, "cherry" => 10];
  ksort($inventory);

  print_r($inventory);
  // Array ( [apple] => 50 [banana] => 30 [cherry] => 10 )
?>

Adding and Removing Elements

array_push() — Add to End

<?php
  $cart = ["laptop", "mouse"];
  array_push($cart, "keyboard", "monitor");

  print_r($cart);
  // Array ( [0] => laptop [1] => mouse [2] => keyboard [3] => monitor )
?>

array_pop() — Remove from End

<?php
  $stack = ["first", "second", "third"];
  $removed = array_pop($stack);

  echo $removed;       // Outputs: third
  echo count($stack);  // Outputs: 2
?>

array_shift() — Remove from Beginning

<?php
  $queue = ["first", "second", "third"];
  $served = array_shift($queue);

  echo $served;       // Outputs: first
  echo $queue[0];     // Outputs: second (now the first element)
?>

array_unshift() — Add to Beginning

<?php
  $list = ["second", "third"];
  array_unshift($list, "first");

  echo $list[0];   // Outputs: first
?>

Merging and Slicing

array_merge() — Combine Arrays

<?php
  $fruits = ["apple", "banana"];
  $veggies = ["carrot", "broccoli"];

  $combined = array_merge($fruits, $veggies);
  print_r($combined);
  // Array ( [0] => apple [1] => banana [2] => carrot [3] => broccoli )
?>

array_slice() — Extract a Portion

<?php
  $letters = ["a", "b", "c", "d", "e", "f"];

  $portion = array_slice($letters, 2, 3);   // Start at index 2, take 3 items
  print_r($portion);
  // Array ( [0] => c [1] => d [2] => e )
?>

Searching Arrays

in_array() — Check if Value Exists

<?php
  $roles = ["admin", "editor", "viewer"];

  if (in_array("editor", $roles)) {
    echo "Editor role found.";
  }
?>

array_search() — Find the Key of a Value

<?php
  $colors = ["red", "green", "blue", "yellow"];
  $position = array_search("blue", $colors);

  echo $position;   // Outputs: 2  (index of "blue")
?>

array_key_exists() — Check if Key Exists

<?php
  $settings = ["theme" => "dark", "language" => "en"];

  if (array_key_exists("theme", $settings)) {
    echo "Theme setting: " . $settings["theme"];
  }
?>

Transforming Arrays

array_map() — Apply a Function to Each Element

<?php
  $prices = [10, 20, 30, 40];

  $discounted = array_map(function($price) {
    return $price * 0.9;   // Apply 10% discount
  }, $prices);

  print_r($discounted);
  // Array ( [0] => 9 [1] => 18 [2] => 27 [3] => 36 )
?>

array_filter() — Keep Only Elements That Pass a Test

<?php
  $numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];

  $evens = array_filter($numbers, function($n) {
    return $n % 2 === 0;
  });

  print_r($evens);
  // Array ( [1] => 2 [3] => 4 [5] => 6 [7] => 8 [9] => 10 )
?>

array_reduce() — Reduce Array to a Single Value

<?php
  $amounts = [100, 250, 75, 300];

  $total = array_reduce($amounts, function($carry, $item) {
    return $carry + $item;
  }, 0);   // 0 is the starting value

  echo $total;   // Outputs: 725
?>

Other Useful Functions

<?php
  $numbers = [3, 1, 4, 1, 5, 9, 2, 6];

  echo array_sum($numbers);      // Outputs: 31 (sum of all elements)
  echo count($numbers);          // Outputs: 8  (number of elements)

  $unique = array_unique($numbers);
  print_r($unique);
  // Array ( [0] => 3 [1] => 1 [2] => 4 [4] => 5 [5] => 9 [6] => 2 [7] => 6 )

  $reversed = array_reverse($numbers);
  echo $reversed[0];   // Outputs: 6 (last element is now first)

  $flipped = array_flip(["a" => 1, "b" => 2, "c" => 3]);
  print_r($flipped);
  // Array ( [1] => a [2] => b [3] => c ) — keys and values are swapped
?>

Key Points

• sort() and rsort() sort indexed arrays; asort() and ksort() sort associative arrays while preserving keys.
• array_push() and array_pop() add and remove from the end; array_shift() and array_unshift() operate on the beginning.
• array_merge() combines arrays; array_slice() extracts a portion.
• in_array() checks for a value; array_search() returns the key of a found value.
• array_map() transforms each element; array_filter() keeps elements that pass a test.
• array_sum() returns the total; array_unique() removes duplicate values.