Blank page if I declare(strict_types=1); in PHP 7 at top of the file

Question

Recently I was checking out on PHP 7, specifically return type declaration and type hinting. I have compiled PHP 7 from source(master branch from Github) and running it in Ubuntu 14.04 virtual box. I tried to run following code to get a test of new Exceptions. But it Gave a blank page.

<?php

function test(): string {

    return [];
}

echo test();

Then I realize I have to set error to be displayed on screen. So I added old fashioned ini_set('display_errors', 1); like below,

<?php
ini_set('display_errors', 1);

function test(): string {

    return [];
}

echo test();

that gave me following TypeError as expected according to this Throwable interface RFC

Fatal error: Uncaught TypeError: Return value of test() must be of the type string, array returned in /usr/share/nginx/html/test.php on line 7 in /usr/share/nginx/html/test.php:7 Stack trace: #0 /usr/share/nginx/html/test.php(10): test() #1 {main} thrown in /usr/share/nginx/html/test.php on line 7

Digging further I added declare(strict_types=1); at the top as below,

<?php declare(strict_types=1);

ini_set('display_errors', 1);

function test(): string {

    return [];
}

echo test();

and bang, error just got disappeared leaving me with blank page. I cant figure out why it is giving me a blank page?

Answer 1

After searching around the google and RFC's I came to follwing sentence in RFC,

This RFC further proposes the addition of a new optional per-file directive, declare(strict_types=1);, which makes all function calls and return statements within a file have “strict” type-checking for scalar type declarations, including for extension and built-in PHP functions.

This means there was nothing wrong with directive declare(strict_types=1) but the problem was the way I was calling ini_set() function. It expects second parameter to be of string type.

string ini_set ( string $varname , string $newvalue )

I was passing int instead, and hence the setting needed to display errors itself failed to set and hence I was hit with a blank page by PHP strict mode. I then changed the code a bit and passed the string "1" as below and it worked.

<?php declare(strict_types=1);

ini_set('display_errors', "1");

function test(): string {

    return [];
}

echo test();