PHP Type Casting Tutorial

Type casting in PHP allows you to convert one data type to another.

While PHP is a loosely typed language and automatically converts data types when needed, explicit type casting is often necessary to ensure proper operations or to meet specific requirements.

This tutorial covers:

1. Basics of Type Casting

Type casting explicitly changes a value from one data type to another. For example, you might want to cast a string containing numbers into an integer for mathematical operations.

Example: Automatic vs Explicit Type Conversion

<?php
$number = "100";
echo gettype($number) . "\n";  // string

$number += 50;                // PHP automatically converts to integer
echo gettype($number) . "\n";  // integer
echo $number . "\n";           // 150
?>

Output:

string
integer
150

2. Type Casting Syntax

Use parentheses with the desired data type before the variable or value to perform explicit type casting.

Supported Types:

• (int) or (integer)
• (bool) or (boolean)
• (float), (double), or (real)
• (string)
• (array)
• (object)
• (unset) (used to cast a value to NULL)

Example: Basic Type Casting Syntax

<?php
$var = "123.45";

$intVar = (int)$var;         // Cast to integer
$floatVar = (float)$var;     // Cast to float
$stringVar = (string)$var;   // Cast to string

echo $intVar . "\n";         // 123
echo $floatVar . "\n";       // 123.45
echo $stringVar . "\n";      // "123.45"
?>

3. Casting Between Data Types

a. String to Integer

When casting a string to an integer, PHP keeps only the numeric part of the string. If the string starts with non-numeric characters, the result is 0.

<?php
$str1 = "123abc";
$str2 = "abc123";

echo (int)$str1 . "\n";  // 123
echo (int)$str2 . "\n";  // 0
?>

b. Integer to Float

Casting an integer to a float adds decimal precision.

<?php
$int = 42;

$float = (float)$int;
echo $float . "\n";  // 42.0
?>

c. Array to Object

Casting an array to an object converts array keys into object properties.

<?php
$array = ["name" => "John", "age" => 30];

$object = (object)$array;
echo $object->name . "\n";  // John
echo $object->age . "\n";   // 30
?>

d. Object to Array

Casting an object to an array converts its properties into key-value pairs.

<?php
$object = (object)["name" => "Alice", "age" => 25];

$array = (array)$object;
print_r($array);
?>

Output:

Array
(
    [name] => Alice
    [age] => 25
)

e. Boolean Conversion

PHP treats certain values as true or false when cast to a boolean:

• false: 0, 0.0, “” (empty string), “0”, NULL, [] (empty array)
• true: All other values

<?php
$values = [0, 1, "", "hello", [], [1, 2, 3]];

foreach ($values as $value) {
    echo (bool)$value ? "true\n" : "false\n";
}
?>

Output:

false
true
false
true
false
true

4. Type Casting with settype()

The settype() function changes the type of a variable in place.

Syntax:

settype($variable, "type");

Example: Using settype()

<?php
$var = "456";

settype($var, "integer");
echo gettype($var) . ": $var\n";  // integer: 456

settype($var, "string");
echo gettype($var) . ": $var\n";  // string: 456
?>

5. Practical Examples

Example 1: Sanitizing User Input

When dealing with user input, ensure that numeric values are properly cast to integers.

<?php
$userInput = "123abc";

$age = (int)$userInput;  // Sanitize input
echo "Age: $age\n";      // Age: 123
?>

Example 2: Array to Object Conversion for API Responses

<?php
$response = ["status" => "success", "data" => ["id" => 101, "name" => "John"]];

$responseObject = (object)$response;
echo $responseObject->status . "\n";  // success
echo $responseObject->data["name"] . "\n";  // John
?>

Example 3: Validating Boolean Input

<?php
$userInput = "yes";

$isValid = (bool)$userInput;
echo $isValid ? "True\n" : "False\n";  // True
?>

Example 4: Type Casting in Arithmetic Operations

<?php
$val1 = "10";
$val2 = 20;

$sum = (int)$val1 + $val2;  // Explicit cast to ensure addition
echo "Sum: $sum\n";         // Sum: 30
?>

Example 5: JSON Data Conversion

<?php
$jsonData = '{"name": "Alice", "age": 25}';

$object = json_decode($jsonData);  // JSON string to object
$array = (array)$object;          // Object to array

echo $object->name . "\n";        // Alice
print_r($array);                  // Array
?>

Output:

Alice
Array
(
    [name] => Alice
    [age] => 25
)

Summary of Type Casting in PHP

Key Takeaways

1. Type casting is essential for data consistency in PHP.
2. Use explicit type casting or settype() when dealing with dynamic or user-provided data.
3. PHP automatically converts types in many scenarios, but explicit type casting ensures precision.