PHP Basics›Core· 30 min read

Operators

Do maths and comparisons — the building blocks of logic.

What you will learn

Use arithmetic operators
Compare values
Combine conditions

Arithmetic & assignment

Operators are the symbols that do work on values — adding, subtracting, comparing. The arithmetic ones (+ - * /) do everyday maths. The example below also shows % (remainder) and the += shortcut.

Arithmetic and assignment shortcuts

<?php
  $a = 10;
  $b = 3;
  echo $a + $b;   // 13
  echo $a % $b;   // 1  (remainder)
  $a += 5;        // $a is now 15
?>

Walking through it: $a + $b adds 10 and 3 to give 13. $a % $b is the modulo operator — it gives the remainder after dividing (10 ÷ 3 is 3 with 1 left over, so the answer is 1). The last line, $a += 5, is shorthand for $a = $a + 5, so $a grows from 10 to 15.

Note: Output (in the browser): 131 The two echo values print next to each other with nothing between them: 13 then 1. The $a += 5 line only changes the variable; it does not print anything by itself.

Tip: The % (remainder) operator is the classic way to test even/odd: if $n % 2 is 0 the number is even, otherwise it is odd.

Comparison & logical

Comparison operators ask a yes/no question about two values and answer with true or false. Logical operators (&&, ||) join several yes/no answers together. These are what every if statement relies on.

Operator	Means
`==`	Equal in value
`===`	Equal in value AND type (preferred)
`!=`	Not equal
`>` `<` `>=` `<=`	Comparisons
`&&` / `and`	AND
`\|\|` / `or`	OR

Here they are in action. A comparison gives back true or false; true prints as 1 and false prints as nothing, so we wrap them in words to make the result clear:

Comparisons and AND in action

<?php
  $age = 20;
  var_dump($age > 18);          // bool(true)  — 20 is greater than 18
  var_dump($age === 20);        // bool(true)  — same value and type
  var_dump($age === "20");      // bool(false) — value matches but type does not
  var_dump($age > 18 && $age < 30);  // bool(true) — both sides are true
?>

Note: Output (in the browser): bool(true) bool(true) bool(false) bool(true) var_dump() is a handy tool that prints a value *with its type* so you can see exactly what came back. Notice line 3: 20 (a number) is not strictly equal to "20" (text), so === gives false. The last line is true only because both $age > 18 AND $age < 30 are true.

Tip: Prefer === over == — it also checks the type, avoiding surprises (e.g. 0 == "abc" behaves oddly in PHP, but === is strict and safe).

Q. Which operator checks both value AND type?

Answer: === is the strict comparison (value and type). Prefer it over == to avoid PHP’s loose-comparison surprises.

✍️ Practice

Calculate the total price of items and print it.
Compare two numbers with === and print whether they are equal.

🏠 Homework

Write a script that checks if a number is even using %.