palindrome.php

<?php

class Palindrome
{
    /**
     * @param  string $str
     *
     * @return bool
     *
     * @throws Exception
     */
    public static function isPalindrome($str)
    {
        if (! is_string($str) || empty($str)) {
            throw new \Exception(
                sprintf('Bad input! Non-empty string expected! %s given', $str)
            );
        }

        $cleanedStr = strtolower(
            preg_replace("/[^a-zA-Z]+/", "", $str)
        );

        $strArray = str_split($cleanedStr);

        return $strArray === array_reverse($strArray);
    }
}

class PalindromeTest extends \PHPUnit_Framework_TestCase
{
    /**
     * @dataProvider palindromes
     */
    public function testIsPalindromeOnSuccess($str)
    {
        $this->assertTrue(Palindrome::isPalindrome($str));
    }

    /**
     * @dataProvider nonPalindromes
     */
    public function testIsPalindromeOnFailure($str)
    {
        $this->assertFalse(Palindrome::isPalindrome($str));
    }

    /**
     * @expectedException \Exception
     *
     * @dataProvider badData
     */
    public function testIsPalindromeWhenItThrowsAnException($str)
    {
        Palindrome::isPalindrome($str);
    }

    public function palindromes()
    {
        return [
            'palindrome_1' => ['noel sees leon'],
            'palindrome_2' => ['Noel Sees Leon'],
        ];
    }


    public function nonPalindromes()
    {
        return [
            'non-palindrome_1' => ['String that s not a palindrome'],
            'non-palindrome_2' => ['null'],
        ];
    }

    public function badData()
    {
        return [
            'bad_data_empty' => [''],
            'bad_data_null' => [null],
            'bad_data_-1'   => [-1]
        ];
    }
}

// For testing purposes (do not submit uncommented):
echo Palindrome::isPalindrome('Noel sees Leon.'). "\n";