Operators in PHP Explained

Operators in PHP

Operators are symbols that perform actions on values, such as adding numbers, comparing two values, or combining conditions. PHP groups them into a few clear categories, and once you know these, most expressions in PHP become easy to read.

Arithmetic operators

These perform basic maths.

<?php
$a = 10;
$b = 3;

echo $a + $b;   // 13  addition
echo $a - $b;   // 7   subtraction
echo $a * $b;   // 30  multiplication
echo $a / $b;   // 3.333... division
echo $a % $b;   // 1   modulus (remainder)
echo $a ** $b;  // 1000 exponent (10 to the power 3)
?>

Assignment operators

The = sign assigns a value. Combined operators are shortcuts.

<?php
$total = 100;

$total += 20;  // same as $total = $total + 20  -> 120
$total -= 10;  // -> 110
$total *= 2;   // -> 220

echo $total;
?>

Comparison operators

These compare two values and return a boolean (true or false). The most important distinction for beginners is == versus ===.

<?php
var_dump(5 == "5");   // true  -> loose: compares value only
var_dump(5 === "5");  // false -> strict: value AND type must match

var_dump(10 != 8);    // true  -> not equal
var_dump(10 > 8);     // true
var_dump(10 <= 10);   // true
?>

• == checks if values are equal after type juggling.
• === checks if values and types are equal. Prefer === to avoid surprises.

The spaceship operator

The <=> operator returns -1, 0, or 1 depending on whether the left value is less than, equal to, or greater than the right. It is handy for sorting.

<?php
echo 1 <=> 2;  // -1 (left is smaller)
echo 2 <=> 2;  //  0 (equal)
echo 3 <=> 2;  //  1 (left is greater)
?>

Logical operators

These combine boolean conditions.

<?php
$loggedIn = true;
$isAdmin  = false;

// AND: both must be true
var_dump($loggedIn && $isAdmin);  // false

// OR: at least one must be true
var_dump($loggedIn || $isAdmin);  // true

// NOT: reverses a boolean
var_dump(!$isAdmin);              // true
?>

String operators

PHP uses the dot (.) to join strings together (concatenation).

<?php
$first = "Web";
$second = "Development";

echo $first . " " . $second; // Web Development

$first .= " Design";          // append to the existing string
echo $first;                  // Web Design
?>

The null coalescing operator

?? returns the left value if it exists and is not null, otherwise the right value. It is great for default values.

<?php
// Imagine $username may or may not be set.
$displayName = $username ?? "Guest";
echo $displayName; // "Guest" if $username is not set
?>

Operator precedence

Like in maths, some operators run before others. Multiplication happens before addition, for example. When in doubt, use parentheses to make the order explicit and readable.

<?php
echo 2 + 3 * 4;     // 14 (multiplication first)
echo (2 + 3) * 4;   // 20 (parentheses first)
?>

Common mistakes

• Using == when you mean ===. Loose comparison can match values you did not intend, such as 0 == "abc" behaviour across versions.
• Confusing = (assignment) with == (comparison). if ($x = 5) assigns rather than compares.
• Forgetting the dot for string joining. PHP uses ., not +, to concatenate strings.
• Relying on precedence instead of parentheses. Parentheses make intent obvious.

FAQ

When should I use === over ==? Almost always prefer ===. It avoids type-juggling surprises by requiring both value and type to match.

What does % do? It returns the remainder of a division. For example, 10 % 3 is 1.

What is ?? used for? It supplies a default value when a variable is null or not set, keeping code short and safe.

Keep learning

Back to the PHP & MySQL hub, revisit Variables & Data Types in PHP, or continue to Control Flow in PHP.

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