Aim

To perform explicit type casting of PHP variables between scalar and compound types — string, int, float, bool, array and object — and verify the exact conversion rules the engine applies.

Theory

PHP is dynamically typed: a variable's type is whatever its current value is, and the engine freely performs type juggling (implicit conversion) inside expressions. Explicit casting overrides this with a cast operator placed before the value: (int), (float), (string), (bool), (array), (object).

Conversion rules exercised by this practical:

• String → int: PHP parses the leading numeric portion and stops at the first invalid character, so (int) "123.45" yields 123 — the fraction is truncated, never rounded.
• String → float: full numeric parse — (float) "123.45" gives 123.45.
• → bool: exactly these values become false: 0, 0.0, "", "0", null, []. Everything else — including "0.0" and "false" — becomes true.
• Scalar → array: the value is wrapped as element [0 => value].
• Associative array → object: produces a stdClass whose properties are the array keys, read with the -> operator.
• Related tooling: settype($var, "integer") converts in place; gettype() / var_dump() inspect types; intval(), floatval(), strval() are the function forms; declare(strict_types=1) switches scalar parameter coercion off so mismatches throw TypeError.

Requirements

• XAMPP with PHP 8.x, or the PHP CLI
• VS Code (or any editor), browser or terminal

Procedure

1. Start Apache in the XAMPP Control Panel.
2. Save the snippet as p03_type_casting.php inside C:\xampp\htdocs\wbplab.
3. Open http://localhost/wbplab/p03_type_casting.php in the browser (optionally wrap output in <pre> for clean formatting) or run php p03_type_casting.php.
4. Experiment: cast "12abc", "abc", "0" and 3.99 to different types, predicting each result before running.

Explanation of the Code

• $numString = "123.45" is the source value. $asInt = (int) $numString truncates to 123, while $asFloat = (float) $numString preserves 123.45.
• $asString = (string) $asInt converts the integer back to the text "123" — the round trip has permanently lost the decimal part.
• $asBool = (bool) $boolString casts "1" to true; the ternary prints the word true because echo would otherwise render boolean true as a bare 1.
• $asArray = (array) $asInt produces [0 => 123], displayed with print_r().
• $asObject = (object) ["name" => "Aman", "age" => 20] builds a stdClass; the interpolated string reads its members as $asObject->name and $asObject->age.

Expected Output

• Original string: 123.45
• Cast to int: 123
• Cast to float: 123.45
• Int back to string: 123
• String to bool: true
• Int to array: Array ( [0] => 123 ) — print_r spreads this over several lines
• Array to object sample: Aman, 20

🎯 Viva Questions

1. What does (int) "123.45" return? 123 — leading numeric parse followed by truncation toward zero.
2. List the values that cast to false. 0, 0.0, "", "0", null, [].
3. Casting vs settype()? A cast returns a converted copy; settype() mutates the variable in place.
4. Which class does (object) create? stdClass, PHP's generic empty class.
5. Type juggling vs type casting? Juggling is implicit engine conversion inside expressions; casting is programmer-forced.
6. What does declare(strict_types=1) change? Scalar type declarations stop coercing; a wrong argument type throws a TypeError.

CO Mapping

CO1, CO2