Aim

To demonstrate PHP's for loop — the counter-controlled, entry-checked iteration construct — by printing the numbers 1 to 5.

Theory

The for loop packs the three pieces of counter management into one header:

for (initialization; condition; increment) { body }

• Initialization runs exactly once, before anything else ($i = 1).
• Condition is tested before every iteration — making for an entry-controlled loop; if it is false on the very first test, the body never runs (zero-iteration case).
• Increment runs after each body execution, then the condition is re-tested.

Advanced notes:

• All three header sections are optional — for (;;) is a deliberate infinite loop, exited with break.
• Each section may hold multiple comma-separated expressions: for ($i = 0, $j = 10; $i < $j; $i++, $j--).
• $i++ (post-increment) and ++$i (pre-increment) are equivalent in the header because the expression value is discarded.
• Off-by-one errors are the dominant bug class: $i <= 5 runs 5 times, $i < 5 runs 4 — always reason about the boundary.
• for is ideal when the number of iterations is known in advance; when it depends on data (file lines, DB rows), while fits better; for arrays, foreach is idiomatic.
• break exits the loop entirely, continue jumps to the increment step of the next iteration.

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 p05a_for.php in C:\xampp\htdocs\wbplab.
3. Execute via http://localhost/wbplab/p05a_for.php or php p05a_for.php.
4. Modify the header — start at 10, count down with $i--, or step by 2 with $i += 2 — and verify your prediction of the output each time.

Explanation of the Code

• echo "FOR LOOP:\n"; prints the heading; \n is a newline in the double-quoted string (use <br> when rendering to HTML).
• The header for ($i = 1; $i <= 5; $i++) initialises the counter to 1, keeps looping while it is at most 5, and bumps it by one after every pass.
• The body echo $i . " "; concatenates the current counter with a space using the . operator, producing the sequence on one line.
• Execution order for each pass is: condition → body → increment; after $i becomes 6 the condition fails and control leaves the loop.

Expected Output

FOR LOOP:
1 2 3 4 5

The counter values appear on a single line separated by spaces.

🎯 Viva Questions

1. Why is for called entry-controlled? Its condition is evaluated before every iteration, including the first.
2. Exact execution order of the header parts? Initialization once; then condition → body → increment, repeated.
3. How many times does for ($i = 0; $i < 5; $i++) run? Five times, for i = 0..4.
4. What does for (;;) mean? All sections empty — an infinite loop, usually exited by break.
5. break vs continue? break leaves the loop; continue skips to the next iteration's increment.
6. When would you pick while over for? When the iteration count is unknown in advance, e.g. reading rows until a query is exhausted.

CO Mapping

CO1, CO2