PHP Booleans

A boolean represents one of two possible values: true or false.

Booleans are the simplest data type. They hold only true or false and are used constantly in conditional testing.

Truthy and falsy

When a non-boolean value is used in a boolean context, PHP converts it. The following are treated as false: 0, 0.0, "", "0", an empty array, and NULL. Almost everything else is true.

Example

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When to use it

  • Toggle a user's account active flag in a database with a boolean column.
  • Gate access to an admin panel by checking a $isAdmin boolean returned from a session.
  • Use the boolean return value of file_put_contents() to detect write failures.

More examples

Boolean literals in conditions

Boolean variables keep condition expressions readable and avoid magic numbers like 1/0 in logic checks.

Example · php
<?php
$isLoggedIn = true;
$isBanned   = false;

if ($isLoggedIn && !$isBanned) {
    echo "Welcome back!";
}

Truthy and falsy values

PHP casts many values to boolean implicitly; knowing which are falsy prevents subtle if-statement bugs.

Example · php
<?php
var_dump((bool) 0);    // false
var_dump((bool) "");   // false
var_dump((bool) []);   // false
var_dump((bool) null); // false

var_dump((bool) 1);    // true
var_dump((bool) "hi"); // true

Strict boolean comparison

Using !== false avoids the falsy-zero trap when a function can legitimately return position 0.

Example · php
<?php
$result = strpos("hello world", "world");

if ($result !== false) {
    echo "Found at position: $result";
}

Related

php comparison operatorsphp if else

Discussion

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