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php 7 – PHP7 Adding a slash to all standard php functions php-cs-fixer rule

Posted by: admin July 12, 2020 Leave a comment


Inherited a PHP7 project. The previous developer added a slash to all standard PHP functions even for \true. Is there any reason for doing this?

Some examples:

\array_push($tags, 'master');

if ($result === \true) {}

$year = \date('Y');

What is the php-cs-fixer rule to toggle this option?

How to&Answers:

As other answers have pointed out, prefixing global or built in functions and constants with \ makes sure they are not over-ridden by declarations within the current namespace. An alternative with the same effect is to add use function foo; and use constant foo; lines at the top of your file.

In most cases, this is unnecessary, as PHP will fall back to the global / built in version where no namespace-local version exists, but there are a few cases where there is a performance advantage if PHP knows in advance which is being used (see issue 3048 and issue 2739 in PHP-CS-Fixer).

The option to control this in PHP-CS-Fixer is native_function_invocation.


You can use the slash to make sure you are using the native PHP function or constant and not the function / constant with the same name defined in a namespace of the project.

namespace test;

function array_push($arr, $str) {
    return $str;

$arr = [];

var_dump(array_push($arr, 'Hello World'));   // array_push defined in namespace test
var_dump(\array_push($arr, 'Hello World'));  // native array_push function

demo: https://ideone.com/3xoFhm

Another case why you can use the \ slash is to speed up the resolving (as mentioned on the PHP-CS-Fixer documentation). PHP doesn’t need to use the autoloader to find the function or constant declaration. So with leading \ PHP can use native function without additional checks.

You can toggle this option on the PHP-CS-Fixer with the native_function_invocation (for functions) and native_constant_invocation (for constants) option. You can find an explanation of the options on the following page: https://github.com/FriendsOfPHP/PHP-CS-Fixer


It could also have been because of performance.
When calling it directly from the root namespace performance is considerably faster.


namespace App;

class Test 
    public function test()
        $first = microtime(true);
        for ($i = 0; $i <= 5000; $i++) {
            echo number_format($i).PHP_EOL;
        echo microtime(true) - $first;

    public function testNative()
        $first = microtime(true);
        for ($i = 0; $i <= 5000; $i++) {
             echo \number_format($i).PHP_EOL;
        echo microtime(true) - $first;

$t = new Test();



The above answer answers your first part, as for cs-fixer the options are:





Because of namespace.

Add \ will find name from global space.

Here is a example:


namespace Foo;

function time() {
    return "my-time";

echo time(), " vs", \time();

You will get result like this:

my-time vs 1553870392


Prefixing a native PHP function with \ will specify that it is required from the global namespace.

As of PHP 7, some native functions are replaced by opcodes if they are called using the FQDN. OpCache is the hot topic when it comes to PHP 7 anyway.

By no means do all native PHP functions need this though.

For those who use PHPStorm, I recommend the Php Inspections (EA Extended) plugin which can inspect your entire project and find these optimizations for you.