Type casting in PHP refers to the explicit conversion of a variable from one data type to another. This is useful when you need to ensure that a variable is treated as a specific type, such as converting a string to an integer, or when performing operations that require a certain type. PHP is a loosely typed language, meaning that variables can change their type dynamically, but type casting allows you to enforce a specific type in your code.

1. Basic Syntax for Type Casting

To cast a variable to a different type, you place the desired type in parentheses before the variable.

• Syntax:

  $variable = (new_type) $variable;
  

• Example:

  <?php
  $str = "10";
  $int = (int) $str; // Casts $str to an integer
  echo $int; // Outputs: 10
  ?>
  

2. Types of Type Casting

a) Casting to Integer

You can cast a variable to an integer using (int) or (integer).

• Example:

  <?php
  $float = 3.14;
  $int = (int) $float; // $int becomes 3
  echo $int; // Outputs: 3
  ?>
  

  • Strings containing numeric values will be cast to their integer equivalent.
  • Non-numeric strings will be cast to 0.

  <?php
  $str = "123abc";
  $int = (int) $str; // $int becomes 123
  echo $int; // Outputs: 123
  ?>
  

b) Casting to Float

You can cast a variable to a float (also known as double or real) using (float), (double), or (real).

• Example:

  <?php
  $int = 42;
  $float = (float) $int; // $float becomes 42.0
  echo $float; // Outputs: 42
  ?>
  

c) Casting to String

You can cast a variable to a string using (string).

• Example:

  <?php
  $num = 123;
  $str = (string) $num; // $str becomes "123"
  echo $str; // Outputs: 123
  ?>
  

  • When casting an array to a string, it will result in the string "Array".
  • When casting an object to a string, PHP attempts to call the __toString() method if it exists.

d) Casting to Boolean

You can cast a variable to a boolean using (bool) or (boolean).

• Example:

  <?php
  $num = 0;
  $bool = (bool) $num; // $bool becomes false
  echo $bool; // Outputs nothing (false is represented as an empty string)
  ?>
  

  • Values that are considered false include:
    • 0 (integer)
    • 0.0 (float)
    • "" (empty string)
    • "0" (string containing "0")
    • NULL
    • Empty arrays (array())
  • All other values are considered true.

e) Casting to Array

You can cast a variable to an array using (array).

• Example:

  <?php
  $str = "Hello, World!";
  $arr = (array) $str; // $arr becomes array("Hello, World!")
  echo $arr[0]; // Outputs: Hello, World!
  ?>
  

  • When casting an object to an array, the properties of the object will become key-value pairs in the array.

f) Casting to Object

You can cast a variable to an object using (object).

• Example:

  <?php
  $arr = array("name" => "John", "age" => 30);
  $obj = (object) $arr;
  echo $obj->name; // Outputs: John
  ?>
  

  • When casting an array to an object, each key-value pair becomes a property of the object.
  • When casting a scalar value to an object, the value is stored as a property named scalar in a new instance of stdClass.

g) Casting to NULL

PHP does not support casting to NULL, but you can assign NULL directly to a variable.

• Example:

  <?php
  $var = 42;
  $var = NULL; // $var is now NULL
  ?>
  

3. Type Juggling vs. Type Casting

• Type Juggling: PHP automatically changes the type of a variable based on the context in which it is used. For example, adding a string to a number will cause PHP to convert the string to a number before performing the addition.

  <?php
  $result = "10" + 2; // $result is 12 (string "10" is converted to integer 10)
  ?>
  

• Type Casting: Type casting is explicitly telling PHP to convert a variable to a specific type, regardless of the context.

  <?php
  $result = (int) "10" + 2; // $result is 12
  ?>
  

4. Practical Use Cases

• Ensuring Data Type Consistency: Type casting is useful when you need to ensure that variables are of a specific type before performing operations.
• Converting User Input: User input is often received as strings, and type casting can convert these inputs to integers, floats, or other types as needed.
• Working with External Data: When dealing with data from databases, APIs, or files, type casting can ensure that the data is handled correctly according to the expected data type.