如何在php中将字符串与长字符串分开

$shortString = 'This is a short string.';
$longString = 'This is a long string that contains multiple lines. '
            . 'It can be split into smaller parts for readability. '
            . 'Each part is concatenated using the concatenation operator (.) '
            . 'to form the complete long string.';

echo $shortString;
echo $longString;

$longString = <<<EOT
This is a long string that contains multiple lines.
It can be split into smaller parts for readability.
Each part is concatenated using the concatenation operator (.)
to form the complete long string.
EOT;

$longString = <<<'EOT'
This is a long string that contains multiple lines.
It can be split into smaller parts for readability.
Each part is concatenated using the concatenation operator (.)
to form the complete long string.
EOT;

echo $longString;