In all programming languages, operators are used to manipulate or perform operations on variables and values. You have already seen the string concatenation operator “.”

There are many operators used in PHP, so we have separated them into the following categories to make it easier to learn them all.

• Assignment Operators
• Arithmetic Operators
• Comparison Operators
• String Operators
• Combination Arithmetic & Assignment Operators

Assignment Operators

Assignment operators are used to set a variable equal to a value or set a variable to another variable’s value. Such an assignment of value is done with the “=”, or equal character. Example:

• $my_var = 4;
• $another_var = $my_var;

Now both $my_var and $another_var contain the value 4. Assignments can also be used in conjunction with arithmetic operators.

Arithmetic Operators

$addition = 2 + 4; 
$subtraction = 6 - 2; 
$multiplication = 5 * 3; 
$division = 15 / 3; 
$modulus = 5 % 2; 
echo "Perform addition: 2 + 4 = ".$addition."<br />"; 
echo "Perform subtraction: 6 - 2 = ".$subtraction."<br />"; 
echo "Perform multiplication:  5 * 3 = ".$multiplication."<br />"; 
echo "Perform division: 15 / 3 = ".$division."<br />"; 
echo "Perform modulus: 5 % 2 = " . $modulus 
	. ". Modulus is the remainder after the division operation has been performed.  
	In this case it was 5 / 2, which has a remainder of 1.";

Display:

Comparison Operators

Comparisons are used to check the relationship between variables and/or values. If you would like to see a simple example of a comparison operator in action, check out our If Statement Lesson. Comparison operators are used inside conditional statements and evaluate to either true or false. Here are the most important comparison operators of PHP.
Assume: $x = 4 and $y = 5;

String Operators

As we have already seen in the Echo Lesson, the period “.” is used to add two strings together, or more technically, the period is the concatenation operator for strings.

$a_string = "Hello";
$another_string = " Billy";
$new_string = $a_string . $another_string;
echo $new_string . "!";

Display:

Combination Arithmetic & Assignment Operators

In programming it is a very common task to have to increment a variable by some fixed amount. The most common example of this is a counter. Say you want to increment a counter by 1, you would have:

• $counter = $counter + 1;

However, there is a shorthand for doing this.

• $counter += 1;

This combination assignment/arithmetic operator would accomplish the same task. The downside to this combination operator is that it reduces code readability to those programmers who are not used to such an operator. Here are some examples of other common shorthand operators. In general, “+=” and “-=” are the most widely used combination operators.

Pre/Post-Increment & Pre/Post-Decrement

This may seem a bit absurd, but there is even a shorter shorthand for the common task of adding 1 or subtracting 1 from a variable. To add one to a variable or “increment” use the “++” operator:

• $x++; Which is equivalent to $x += 1; or $x = $x + 1;

To subtract 1 from a variable, or “decrement” use the “–” operator:

• $x–; Which is equivalent to $x -= 1; or $x = $x – 1;

In addition to this “shorterhand” technique, you can specify whether you want to increment before the line of code is being executed or after the line has executed. Our PHP code below will display the difference.

$x = 4;
echo "The value of x with post-plusplus = " . $x++;
echo "<br /> The value of x after the post-plusplus is " . $x;
$x = 4;
echo "<br />The value of x with with pre-plusplus = " . ++$x;
echo "<br /> The value of x after the pre-plusplus is " . $x;

Display:

As you can see the value of $x++ is not reflected in the echoed text because the variable is not incremented until after the line of code is executed. However, with the pre-increment “++$x” the variable does reflect the addition immediately.

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