1.2.923. PHP 7.4 Reserved Keyword¶
fn is a new PHP keyword. In PHP 7.4, it is used to build the arrow functions. When used at an illegal position, fn generates a Fatal error at compile time.
As a key word, fn is not allowed as constant name, function name, class name or inside namespaces.
fn is fine for method names. It may also be used for constants with define(), and constant() but it is not recommended.
<?php
// PHP 7.4 usage of fn
function array_values_from_keys($arr, $keys) {
return array_map(fn($x) => $arr[$x], $keys);
}
// PHP 7.3 usage of fn
const fn = 1;
function fn() {}
class x {
// This is valid in PHP 7.3 and 7.4
function fn() {}
}
?>
See also PHP RFC: Arrow Functions.
1.2.923.1. Specs¶
Short name |
Php/Php74ReservedKeyword |
Rulesets |
|
Exakat since |
1.9.2 |
PHP Version |
With PHP 7.4 and older |
Severity |
Minor |
Time To Fix |
Quick (30 mins) |
Precision |
Very high |
Available in |