Data Types, Variables and Operators

PHP Data Types

A Data type is the classification of data into a category according to its attributes;

  • Alphanumeric characters are classified as strings
  • Whole numbers are classified integers
  • Numbers with decimal points are classified as floating points.
  • True or false values are classified as Boolean.

PHP is a loosely typed language; it does not have explicit defined data types. PHP determines the data types by analyzing the attributes of data supplied. PHP implicitly supports the following data types

  • Integer – whole numbers e.g. -3, 0, 69. The maximum value of an integer is platform-dependent. On a 32 bit machine, it’s usually around 2 billion. 64 bit machines usually have larger values. The constant PHP_INT_MAX is used to determine the maximum value.
  • loating point number – decimal numbers e.g. 3.14. they are also known as double or real numbers.  The maximum value of a float is platform-dependent. Floating point numbers are larger than integers.
  • Character string – e.g. Hello World
  • Boolean – e.g. True or false.

Before we go into more details discussing PHP data types, let’s first discuss variables.

PHP Variable

A variable is a name given to a memory location that stores data at runtime.

The scope of a variable determines its visibility.

A Php global variable is accessible to all the scripts in an application.

A local variable is only accessible to the script that it was defined in.

Think of a variable as a glass containing water. You can add water into the glass, drink all of it, refill it again etc.

The same applies for variables. Variables are used to store data and provide stored data when needed. Just like in other programming languages, PHP supports variables too. Let’s now look at the rules followed when creating variables in PHP.

  • All variable names must start with the dollar sign e.g.
  • Learn about PHP Variable, Operators and Data types
  • Variable names are case sensitive; this means $my_var is different from $MY_VAR
  • Learn about PHP Variable, Operators and Data types
  • All variables names must start with a letter follow other characters e.g. $my_var1. $1my_var is not a legal variable name.
  • Learn about PHP Variable, Operators and Data types
  • Variable names must not contain any spaces, “$first name” is not a legal variable name. You can instead use an underscore in place of the space e.g. $first_name. You cant use characters such as the dollar or minus sign to separate variable names.
  •  Learn about PHP Variable, Operators and Data types

  Let’s now look at how PHP determines the data type depending on the attributes of the supplied data.

Use of Variables

Variables help separate data from the program algorithms.

The same algorithm can be used for different input data values.

For example, suppose that you are developing a calculator program that adds up two numbers, you can create two variables that accept the numbers then you use the variables names in the expression that does the addition.

Variable Type Casting

Performing arithmetic computations using variables in a language such as C# requires the variables to be of the same data type.

Type casting is converting a variable or value into a desired data type.

This is very useful when performing arithmetic computations that require variables to be of the same data type.

Type casting in PHP is done by the interpreter.

In other languages such as C#, you have to cast the variables. The code below shows type casting in C#.

PHP also allows you to cast the data type. This is known as explicit casting. The code below demonstrates explicit type casting.

Above Code Output 2 The var_dump function is used to determine the data type. The code below demonstrates how to use the var_dump function.

PHP Constant

Define constant– A constant is a variable whose value cannot be changed at runtime.

Suppose we are developing a program that uses the value of PI 3.14, we can use a constant to store its value.

Let’s now look at an example that defines a constant. define(‘PI’,3.14); //creates a constant with a value of 3.14 Once you define PI as 3.14 , writing a code like below will generate an error PI = 4; //PI has been defined as a constant therefore assigning a value is not permissible.

PHP Operators

Arithmetic operators

Arithmetic operators are used to perform arithmetic operations on numeric data. The concatenate operator works on strings values too. PHP supports the following operators.

OperatorNameDescriptionExampleOutput
+AdditionSummation of x and y1 + 1;2
SubtractionDifference between x and y1 – 1;0
*MultiplicationMultiplies x and y3 * 7;21
/DivisionQuotient of x and y45 / 5;9
%Php ModulusGives reminder of diving x and y10 % 3;1
-nNegationTurns n into a negative number-(-5);5
x . yConcatenationPuts together x and y“PHP” . ” ROCKS”;10 . 3;PHP ROCKS103

Assignment Operators

Assignment operators are used to assign values to variables. They can also be used together with arithmetic operators.

OperatorNameDescriptionExampleOutput
x = ?assignmentAssigns the value of x to ?$x = 5;5
x += ?additionIncrements the value of x by ?$x = 2;$x += 1;3
X -= ?subtractionSubtracts ? from the value of x$x = 3;$x -= 2;1
X *=?multiplicationMultiplies the value of x ? times$x = 0;$x *=9;0
X /=?divisionQuotient of x and ?$x = 6;$x /=3;2
X %=?modulusThe reminder of dividing x by?$x = 3;$x %= 2;1
X .=?concatenatePuts together items” $x = ‘Pretty’;$x .= ‘ Cool!’;”Pretty Cool!

Comparison operators

Comparison operators are used to compare values and data types.

OperatorNameDescriptionExampleOutput
X == yEqualCompares x and y then returns true if they are equal1 == “1”;True or 1
X === yidenticalCompares both values and data types.1 === “1”;False or 0. Since 1 is integer and “1” is string
X != y, x <> yPHP Not equalCompares values of x and y. returns true if the values are not equal2 != 1;True or 1
X > yGreater thanCompares values of x and y. returns true if x is greater than y3 > 1;True or 1
X < yLess thanCompares values of x and y. returns true if x is less than y2 < 1;False or 0
X >= yGreater than or equalCompares values of x and y. returns true if x is greater than or equal to y1 >=1True or 1
X <= yLess than or equalCompares values of x and y. returns true if x is greater than or equal to y8 <= 6False or 0

Logical operators

When working with logical operators, any number greater than or less than zero (0) evaluates to true. Zero (0) evaluates to false.

OperatorNameDescriptionExampleOutput
X and y, x && yAndReturns true if both x and y are equal1 and 4;True&& False;True or 1False or 0
X or y, x || yOrReturns true if either x or y is true6 or 9;0 || 0;True or 1False or 0
X xor yExclusive or, xorReturns true if only x is true or only y is true1 xor 1;1 xor 0;False or 0True or 1
!xNotReturns true if x is false and false if x is true!0;True or 1

Summary

  • .  PHP is a loosely typed language.
  • .   Variables are memory locations used to store data
  • .   The value of constants cannot be changed at runtime
  • .   Type casting is used to convert a value or variable into a desired data type
  • .   Arithmetic operators are used to manipulate numeric data
  • .   Assignment operators are used to assign data to variables
  • .   Comparison operators are used to compare variables or values
  • .   Logical operators are used to compare conditions or values
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