PHP Operators (Full Guide)

Operators let you compute values, compare, make decisions, concatenate strings, merge arrays, and more. This page is a complete reference with examples and common pitfalls.

1) Arithmetic Operators

<?php
  $a = 10; $b = 3;
  echo "Add: " . ($a+$b) . "\n";
  echo "Pow: " . ($a**$b);
?>

2) Assignment Operators

Assignment by Reference (&)

<?php
  $a = 10;
  $b =& $a; // $b references $a
  $b = 20;
  echo $a; // 20
?>

3) Increment / Decrement

4) Comparison Operators

Type Juggling Pitfalls (== vs ===)

<?php
  var_dump("0" == 0);          // true (juggled)
  var_dump("0" === 0);         // false (type differs)
  var_dump(""  == 0);          // true (!) 
  var_dump("0" == false);    // true
  // Prefer === and !== for safety
?>

Spaceship (<=>)

<?php
  // -1 if left < right, 0 if equal, 1 if left > right
  echo 2 <=> 3;   // -1
  echo 3 <=> 3;   // 0
  echo 4 <=> 3;   // 1
?>

Null Coalescing (??)

Returns the first operand that exists and isn’t NULL.

<?php
  $name = $_GET['name'] ?? 'Guest';
  echo "Hello, $name";
?>

5) Logical Operators

<?php
  $a = true or false;  // ($a = true) or false → $a is true
  $b = true || false; // $b = (true || false) → $b is true
?>

6) Ternary & Elvis

7) String Operators

8) Array Operators

<?php
  $a = ["id"=>1, "name"=>"A"];
  $b = ["name"=>"B", "age"=>20];
  $u = $a + $b; // ["id"=>1, "name"=>"A", "age"=>20]
  var_dump($u);
?>

9) Bitwise Operators

10) Error Suppression (@)

Prefixing an expression with @ hides error messages from that expression.

<?php
  // not recommended: hides useful errors
  $f = @file_get_contents("missing.txt");
?>

11) instanceof & Nullsafe ?-> (PHP 8)

instanceof checks object type; nullsafe operator avoids errors when a chain is null.

<?php
  class User { public $profile; }
  $u = new User();
  var_dump($u instanceof User);
  $city = $u->profile?->address?->city ?? "Unknown";
?>

12) Execution Operator (Backticks)

Backticks `cmd` execute a shell command and return output (same as shell_exec()).

13) Operator Precedence & Associativity (Essential)

Practice Tasks

1. Use <=> to sort an array of associative users by age, then by name.
2. Given $_GET['page'], safely compute $page as an integer defaulting to 1 using ?? and casting.
3. Demonstrate the difference between and vs && in an assignment expression.
4. Merge two arrays with the + operator and with array_merge(); explain the difference in keys.
5. Build a permission flags integer using bitwise operators, and test for a flag with &.