Integer type validation of a PHP variable

Published on 2024-01-19 • Modified on 2024-01-19

In a previous snippet, we saw a (ugly) hack to convert a string variable to an integer. Here, we validate with the multi-purpose filter_var() function. If the variable is not an integer, then it returns false. The specific case for true is something to know as it returns true even if it's a boolean. As we can see in the output, true is transformed to 1. It is weird as it is not the case for false.

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<?php

declare(strict_types=1);

namespace App\Controller\Snippet;

/**
 * I am using a PHP trait to isolate each snippet in a file.
 * This code should be called from a Symfony controller extending AbstractController (as of Symfony 4.2)
 * or Symfony\Bundle\FrameworkBundle\Controller\Controller (Symfony <= 4.1).
 * Services are injected in the main controller constructor.
 */
trait Snippet287Trait
{
    public function snippet287(): void
    {
        $tests = [
            true,
            false,
            '0.0',
            'foo',
            ['my' => 'array'],
            555,
            0,
            1,
            -1,
        ];

        foreach ($tests as $test) {
            $filteredVar = filter_var($test, FILTER_VALIDATE_INT);
            if ($filteredVar !== false) {
                echo \sprintf('%s is an integer, final var: %s'.PHP_EOL, var_export($test, true), var_export($filteredVar, true));
            } else {
                echo \sprintf('%s is NOT an integer'.PHP_EOL, var_export($test));
            }
        }

        // That's it! 😁
    }
}

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