experiments.php

<?php

declare(strict_types=0);

class Test {
    private array $array;
    private string $string;
    
    public function __construct()
    {
        // $this->array = 1; // Fatal error
        $this->array = (array) 1; // ok, [1]
        $this->string = 1; // ok, '1'
        
    }
    
    public function getArray(): array
    {
        return $this->array; // ok
    }
    
    public function getAnotherArray(): array
    {
        // return 1; // Fatal error
        return (array) 1; // ok, [1]
    }
    
    public function getString(): string
    {
        return $this->string;
    }
}

$test = new Test();

var_dump($test->getArray(), $test->getAnotherArray(), $test->getString());

/* var_dump result
array(1) {
  [0]=>
  int(1)
}
array(1) {
  [0]=>
  int(1)
}
string(1) "1"
*/

This code in a sandbox https://3v4l.org/UkmqW