Aim

To traverse a PHP array with the foreach loop, the idiomatic construct for iterating arrays and other traversable structures without manual index bookkeeping.

Theory

foreach ($array as $value) visits every element of an array in insertion order; the richer form foreach ($array as $key => $value) also exposes each element's key. Why it is preferred over an index-based for for arrays:

• It works uniformly on associative arrays, where numeric indexing is meaningless.
• There is no counter to get wrong — no off-by-one class of bugs.
• It iterates anything that is an array or implements Traversable (e.g. Iterator objects, generators, PDO result sets).

Semantics worth knowing at the advanced level:

• Copy semantics: $value receives a copy of each element — assigning to $value does not modify the array.
• Reference form: foreach ($arr as &$value) makes $value an alias, so writes mutate the array in place. Classic pitfall: the reference survives the loop, so a later plain foreach can silently overwrite the last element — always unset($value); after a by-reference loop.
• Keys of a list-style array are 0, 1, 2, ...; foreach follows insertion order, not sorted key order.
• break/continue work exactly as in other loops.

Requirements

• XAMPP/WAMP with PHP 8.x, or PHP CLI
• Code editor and a browser/terminal

Procedure

1. Start Apache from the XAMPP Control Panel.
2. Save the snippet as p05d_foreach.php in C:\xampp\htdocs\wbplab.
3. Run http://localhost/wbplab/p05d_foreach.php or php p05d_foreach.php.
4. Extend the experiment: switch to foreach ($fruits as $index => $fruit) and print $index: $fruit; then try an associative array like ["a" => "Apple"] to see string keys.

Explanation of the Code

• $fruits = ["Apple", "Banana", "Cherry"]; builds an indexed array using short array syntax; implicit keys are 0, 1, 2.
• foreach ($fruits as $fruit) starts a traversal: on each pass PHP copies the next element into $fruit — first "Apple", then "Banana", then "Cherry".
• The body echo $fruit . " "; prints the copy followed by a space; because $fruit is a copy, writing $fruit = "Mango"; inside the loop would leave $fruits untouched.
• The loop ends automatically after the last element — no condition or counter management exists to maintain.

Expected Output

FOREACH LOOP:
Apple Banana Cherry

The three fruits print on one line, space-separated, in insertion order.

🎯 Viva Questions

1. Does assigning to $value inside foreach change the array? No — $value is a copy unless declared with &.
2. What is the danger of foreach ($arr as &$v)? The reference outlives the loop; without unset($v), a later loop can corrupt the last element.
3. How do you access keys during traversal? Use the foreach ($arr as $key => $value) form.
4. In what order does foreach visit elements? Insertion order of the array, regardless of key values.
5. What besides arrays can foreach iterate? Any Traversable — objects implementing Iterator/IteratorAggregate, and generators.
6. When is a classic for still better for arrays? When you need index arithmetic, e.g. comparing $a[$i] with $a[$i + 1] in sorting algorithms.

CO Mapping

CO1, CO2