What is the difference between == and === in PHP 8?

== compares values after type juggling. === compares value and type with no conversion.

The PHP 8 change

PHP 8 changed string and number comparison. Before 8.0, 0 == "abc" was true because "abc" was cast to 0. Since 8.0, if the string is not numeric, the number is cast to a string and compared as strings, so:

var_dump(0 == "abc");      // PHP 7: true,  PHP 8: false
var_dump("1" == "01");     // true  (both numeric strings)
var_dump(100 == "1e2");    // true  (numeric string)
var_dump(null == false);   // true
var_dump([] == false);     // true
var_dump("0" == false);    // true
var_dump("abc" == 0);      // false in PHP 8

Numeric strings with trailing whitespace are now also treated as numeric ("123 " == 123 is true).

Use === by default

if ($status === 'active') {}
if (in_array($id, $allowed, true)) {}     // third argument = strict
if (array_search('x', $list, true) !== false) {}
switch (true) {}                           // or use match

in_array, array_search and array_keys are loose by default, so a classic bug is in_array('abc', [0]) returning true in PHP 7.

Security note: loose comparison of hashes can be exploited ("magic hashes": "0e123" == "0e456" is true because both are numeric strings in scientific notation). Always compare tokens and hashes with hash_equals() and passwords with password_verify().

Useful related tools

• match uses strict comparison and throws UnhandledMatchError if nothing matches.
• The spaceship operator <=> still uses loose comparison rules.
• Add declare(strict_types=1); for strict scalar type checks on function arguments (it does not change ==).

Pitfall: "abc" == 0 fixed in 8.0 may have been hiding in legacy code, so test upgrades with E_ALL and static analysis (PHPStan or Psalm).