🔍 Type Checking in PHP

Type Checking is the process of identifying, inspecting, and validating the data type of PHP variables or incoming data payloads. Verifying data types when working with user forms, databases, or API inputs ensures your application executes safely and without runtime errors.

1️⃣ gettype() Function
Returns the name of the variable's data type as a string.

$number = 42;
$text = "TeachWebCode";

echo gettype($number); // Outputs: integer
echo gettype($text);   // Outputs: string

2️⃣ is_int() / is_integer() - Integer Validation
Checks whether a variable's value is an integer.

$value = 100;

if (is_int($value)) {
    echo "This variable is an integer.";
}

3️⃣ is_string() - String Validation
Verifies whether a variable is a textual string expression.

$name = "Baykuş Hoca";

if (is_string($name)) {
    echo "String value confirmed.";
}

4️⃣ is_numeric() - Numeric Value Validation
Checks if a variable is a number or a numeric string (such as "250"). Exceptionally useful for validating form inputs before processing arithmetic operations.

$input = "450";

if (is_numeric($input)) {
    echo "Input is a valid numeric value."; // Evaluates to true even for string "450"
}

5️⃣ is_array() - Array Validation
Tests whether a variable is structured as an array.

$items = ["HTML", "CSS", "PHP"];

if (is_array($items)) {
    echo "Variable is an array.";
}

6️⃣ is_null() - Null Value Check
Evaluates whether a variable's value is set to null.

$data = null;

if (is_null($data)) {
    echo "Variable is null/empty.";
}

Other essential type validation functions frequently used in PHP applications:

• is_float() / is_double(): Validates floating-point numbers.
• is_bool(): Checks for boolean values (true or false).
• is_object(): Validates instantiated objects.
• is_callable(): Checks if a function, method, or closure can be called dynamically.