# PHP Comparison and Arithmetic Operators

## Basics of PHP – Part 7

**Forward: In this part of the series, we talk about some common PHP Operators.**

By: Chrysanthus Date Published: 28 Jul 2012

### Introduction

Note: If you cannot see the code or if you think anything is missing (broken link, image absent), just contact me at forchatrans@yahoo.com. That is, contact me for the slightest problem you have about what you are reading.

**Operand**

An Operand is a variable or a literal (value) associated with an operator. Consider,

$myVar = 30;

$myVar is a left operand and 30 is a right operand. = is the assignment operator, not the equal operator. The equal operator is, == and is used only in conditions.

Consider:

$myVar && $hisVar && $herVar

There are three operands in the above expression. So, you can talk of the first, second and third operand.

**Comparison Operators**

A comparison operator compares the operands on its sides and returns a logical value depending on whether the comparison is correct or wrong. If the comparison is correct a logical value of true is returned. If it is wrong, a logical value of false is returned. Another name for Boolean Value is Logical Value, which is either true or false.

**The Equal Operator**

We have seen this before. It is ==, typed as a double assignment operator. The equal operator returns true if operands are equal, otherwise it returns false. We have seen many examples of this.

**The Not Equal Operator**

The Not Equal operator is the opposite of the Equal Operator. The Not Equal operator is, != . It returns true if the operands are not equal, otherwise it returns false. Let us look at some examples:

Try the following code (include the HTML components first):

<?php

$myVar = 25;

$hisVar = 30;

if ($myVar != $hisVar)

{

echo 'The values of the two variables are not equal.';

}

?>

$myVar is 25, $hisVar is 30. The condition is read like this: If $myVar is not equal to $hisVar, then the if-block will be executed. Since the values of the variables are not equal, ($myVar != $hisVar) returns true.

In the following code, the values of the two variables are equal, so the condition returns false and the if-block is not executed.

<?php

$myVar = 50;

$hisVar = 50;

if ($myVar != $hisVar)

{

echo 'The values of the two variables are not equal.';

}

?>

Note: The letter O and the digit zero are not the same things. If you type the letter O in place of zero you will not have the right results. The digit zero is found in the number keypad of your keyboard. The letter O is found in the main keyboard area.

**The Greater Than Operator**

The Greater Than operator is, > . It returns true if the left operand is greater than the right operand. In the following example, the left operand is greater than the right operand. So the if-block is executed:

<?php

$variab1 = 60;

$variab2 = 70;

if ($variab2 > $variab1)

{

echo 'The value of variab2 is greater than the value of variab1.';

}

?>

Read and try the above code.

**Greater Than Or Equal - Operator**

The Greater Than or Equal operator is, >= (it is the math greater than sign followed by the math equal sign). It returns true if the left operand is greater than or equal to the right operand.

**The Less Than Operator**

The Less Than Operator is < .It returns true if the left operand is less than the right operand.

**The Less Than or Equal - Operator**

The Less than or Equal operator is, <= . It returns true if the left operand is less than or equal to the right operand.

**Arithmetic Operators**

An Arithmetic operator takes one or two numbers as operands (either literals or variables) and returns the answer, similar to what happens in arithmetic.

The standard arithmetic operators are addition (+), subtraction (-), multiplication (*), and division (/). To save time explaining these four operators, just read and try the following examples:

**Addition Operator**

Code example:

<?php

$var1 = 20;

$var2 = 30;

$var3 = $var2 + $var1;

echo $var3;

?>

</body>

**Subtraction Operator**

Code example:

<?php

$var1 = 20;

$var2 = 30;

$var3 = $var2 - $var1;

echo $var3;

?>

**Multiplication Operator**

Code example:

<?php

$var1 = 20;

$var2 = 30;

$var3 = $var2 * $var1;

echo $var3;

?>

Note that the multiplication operator is * and not X.

**Division Operator**

Code example:

<?php

$var1 = 20;

$var2 = 30;

$var3 = $var2 / $var1;

echo $var3;

?>

Note that the division operator is, / .

Other operators are the Modulus (%), Increment (++), Decrement (--), and the Negation operators. You have to learn the particular way in which each of these operators behaves.

**Modulus Operator**

The modulus operator divides the first operand by the second operand and returns the remainder. Read and try the following code:

<?php

$var1 = 17;

$var2 = 12;

$var3 = $var1 % $var2;

echo $var3;

?>

The Modulus operator is the percentage sign.

**Increment Operator**

The Increment Operator is, ++. It works with one operand, not two as the others. The operand has to be a number. When it is placed in front (prefix) of the operand, it behaves in one way. When it is placed after (postfix) the operand it behaves in another way.

Prefix: When it is prefix, it adds 1 to the operand and returns the incremented operand. Read and try the following code:

<?php

$var1 = 10.5;

$var2 = ++$var1;

echo $var2;

?>

In the code, initially, 10.5 is assigned to var1. Then we have a statement. In the statement you have a new variable, $var2, the assignment operator and then “++$var1”. What interest us here is “++$var1”, where the increment operator is in front of the variable. The value the increment operator returns is assigned to $var2. If you have tried the code, you would have noticed that the value of $var2 is 11.5. This means, if used prefix, it increments the operand and then returns the incremented operand.

Postfix: When it is postfix, it returns the operand before adding 1 to it. The returned value is the original value of the operand. The increased value is the new value of the operand, which is not returned. Read and try the following code.

<?php

$var1 = 10.5;

$var2 = $var1++;

echo $var2; echo "<br />";

echo $var1;

?>

If you have tried the above code, you would have noticed that the value for $var2 is 10.5 and the final value for $var1 is 11.5, confirming that the incrementing took place after the value was returned.

**Decrement Operator**

The Decrement operator, -- , behaves like the increment operator with the only difference that it subtracts 1 instead of adding.

**Negation Operator**

This operator is the negative sign, - . It works with one operand (on its right); it negates the operand just like in math. Read and try the following:

<?php

$myVar = 17;

$hisVar = -$myVar;

echo "$hisVar";

?>

We have come to the end of this part of the series. Rendezvous in the next part.

Chrys

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