How can I add elements to an empty array in PHP?

To add elements to an empty array in PHP, you can use several methods. Below is a detailed explanation with examples:

1. Square Bracket Syntax [] (Recommended for single elements)

• Appends elements to the end of the array.
• Automatically assigns numeric indices starting from 0.
• Efficient for single elements.

   // Initialize an empty array
   $fruits = [];

   // Add elements
   $fruits[] = 'Apple';
   $fruits[] = 'Banana';
   $fruits[] = 'Cherry';

   print_r($fruits);
   /* Output:
   Array
   (
       [0] => Apple
       [1] => Banana
       [2] => Cherry
   )
   */

2. array_push() (Ideal for multiple elements)

• Appends one or more elements to the end of the array.
• Returns the new number of elements.
• Slightly less efficient than [] for single elements but optimal for adding multiple values at once.

   $colors = [];

   // Add one element
   array_push($colors, 'Red');

   // Add multiple elements
   array_push($colors, 'Green', 'Blue');

   print_r($colors);
   /* Output:
   Array
   (
       [0] => Red
       [1] => Green
       [2] => Blue
   )
   */

3. Assign with Specific Index

• Manually set an index for the element.
• Useful for non-sequential keys or associative arrays.
• Avoid gaps in indices to prevent unexpected behavior.

   $languages = [];

   // Add elements with explicit indices
   $languages[0] = 'PHP';
   $languages[1] = 'JavaScript';
   $languages[2] = 'Python';

   // Add with a string key (associative array)
   $languages['backend'] = 'Java';

   print_r($languages);
   /* Output:
   Array
   (
       [0] => PHP
       [1] => JavaScript
       [2] => Python
       [backend] => Java
   )
   */

4. array_unshift() (Prepend to Beginning)

• Adds elements to the start of the array.
• Re-indexes numeric keys (may impact performance for large arrays).
• Original indices are reset starting from 0.

   $stack = ['Middle'];

   // Prepend elements
   array_unshift($stack, 'Start');
   array_unshift($stack, 'New Start');

   print_r($stack);
   /* Output:
   Array
   (
       [0] => New Start
       [1] => Start
       [2] => Middle
   )
   */

Key Considerations:

• Efficiency: Use [] for single elements; array_push() for multiple.
• Indices: Numeric keys auto-increment. Gaps can occur if indices are skipped.
• Associative Arrays: Use explicit keys (e.g., $array['key'] = value).

Example Workflow:

// Start with an empty array
$cart = [];

// Add items
$cart[] = 'Book';          // Index 0
$cart[] = 'Pen';            // Index 1
array_push($cart, 'Ruler', 'Eraser'); // Indices 2, 3
$cart['discount'] = '10%';  // Key 'discount'

print_r($cart);
/* Output:
Array
(
    [0] => Book
    [1] => Pen
    [2] => Ruler
    [3] => Eraser
    [discount] => 10%
)
*/

Best Practices:

• Initialize Arrays: Declare $array = [] before adding elements.
• Avoid Mixing Key Types: Prefer consistent keys (all numeric or all associative).
• Prevent Index Gaps: Use automatic indexing ([] or array_push()) unless explicit keys are needed.