Variables, Data Types & Scope

Dynamic typing, type declarations, and variable scoping rules

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PHP variables always begin with a dollar sign ($) followed by the variable name. PHP is dynamically typed, but modern PHP 7 and 8 provide powerful scalar type declarations.

Variable Rules and Core Types

Variables are case-sensitive: $color, $Color, and $COLOR represent three completely distinct storage slots.

Primary data types include String, Integer, Float, Boolean, Array, Object, Callable, and NULL.

Variable scope in PHP includes local, global, and static. Functions have isolated variable scope by default unless accessed via the global keyword or the $GLOBALS superglobal array.

Variables and Type Casting

Try It Yourself »

<?php
  $user = "Elena Vance";
  $age = 29;               // Integer
  $rating = 4.95;          // Float
  $isSubscribed = true;    // Boolean

  // Type inspection and formatted output
  printf("%s has an account rating of %.2f (Status: %s)\n", 
    $user, 
    $rating, 
    $isSubscribed ? "Active" : "Inactive"
  );

  // Static variable retains state between function calls
  function trackVisits() {
    static $count = 0;
    $count++;
    return $count;
  }
?>

Static variables preserve their values across multiple calls within the same execution cycle.

Type	Example Literal	Description
string	"Hello Codexia"	Text enclosed in single or double quotes
int	42, -100	Whole numbers without decimal points
float	3.14159	Numbers with floating fractional points
bool	true / false	Binary truth values (case-insensitive)
null	null	Special type representing a variable with no value

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Test Yourself With Exercise

+15 XP

Which symbol MUST precede all variable names in PHP?

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