Multiline Strings in PHP

A common task I face when programming is to store multi-line strings in a variable. This may be related to templating for views, emails or configuration files for third party systems, or just writing readable inputs for tests.

The naive approach

First I want to show you the naive approach:

function makeUserJson(): string
{
    return "
      {
        \"name\": \"John Doe\",
        \"email\": \"john@example.org\",
        \"timezone\": \"Europe/Paris\"
      }
    ";
}

echo "start" . PHP_EOL;
echo makeUserJson() . PHP_EOL;
echo "end" . PHP_EOL;

The resulting literal output (notice the extra blank lines and indentation):

start

      {
        "name": "John Doe",
        "email": "john@example.org",
        "timezone": "Europe/Paris"
      }
    
end

Problems in the output:

• there are additional blank lines above and below the json object
• the level of indentation of the result depends on the level of indentation in your source code
• the extra whitespace may lead to unexpected behavior when further processing the string
• we have to escape quotes with backslashes

Using Heredoc

Here's how you can fix all of the above problems with Heredoc:

function makeUserJson2(): string
{
    return <<<JSON
      {
        "name": "John Doe",
        "email": "john@example.org",
        "timezone": "Europe/Paris"
      }
      JSON;
}

echo "start" . PHP_EOL;
echo makeUserJson2() . PHP_EOL;
echo "end" . PHP_EOL;

The result:

start
{
  "name": "John Doe",
  "email": "john@example.org",
  "timezone": "Europe/Paris"
}
end

• additional whitespace on the left is removed and no longer depends on its position in the source code
• no extra blank lines are added
• no need to escape quotes

Variable Support

You can use variables inside your multi-line strings:

function makeUserJson3(string $name): string
{
    return <<<JSON
      {
        "name": "$name",
        "email": "jane@example.org",
        "timezone": "Europe/Paris"
      }
      JSON;
}

echo makeUserJson3("Jane White");

In the result, $name is replaced with the concrete value:

{
  "name": "Jane White",
  "email": "jane@example.org",
  "timezone": "Europe/Paris"
}

Disabling Interpolation with Nowdoc

If you do not want the string to be interpolated, use Nowdoc instead, by adding single quotes to the start marker:

function makeUserJson3(): string
{
    return <<<'JSON'
      {
        "name": "$name",
        "email": "jane@example.org",
        "timezone": "Europe/Paris"
      }
      JSON;
}

echo makeUserJson3();

In the result, $name is written out literally, because we disabled interpolation:

{
  "name": "$name",
  "email": "jane@example.org",
  "timezone": "Europe/Paris"
}

Summary

In this blog post, you learned how to create multi-line strings in PHP, without the need for worrying about escaping quotes or indentation of source code, with variable interpolation (Heredoc) or without (Nowdoc).