Use a backslash as such

"From time to \"time\"";

Backslashes are used in PHP to escape special characters within quotes. As PHP does not distinguish between strings and characters, you could also use this

'From time to "time"';

The difference between single and double quotes is that double quotes allows for string interpolation, meaning that you can reference variables inline in the string and their values will be evaluated in the string like such

$name = 'Chris';
$greeting = "Hello my name is $name"; //equals "Hello my name is Chris"

As per your last edit of your question I think the easiest thing you may be able to do that this point is to use a 'heredoc.' They aren't commonly used and honestly I wouldn't normally recommend it but if you want a fast way to get this wall of text in to a single string. The syntax can be found here: http://www.php.net/manual/en/language.types.string.php#language.types.string.syntax.heredoc and here is an example:

$someVar = "hello";
$someOtherVar = "goodbye";
$heredoc = <<<term
This is a long line of text that include variables such as $someVar
and additionally some other variable $someOtherVar. It also supports having
'single quotes' and "double quotes" without terminating the string itself.
heredocs have additional functionality that most likely falls outside
the scope of what you aim to accomplish.
term;

Example 1: Variable between single quotes

If you use single quotes everything between them will always be treated as part of the string.

$output .= '<div class="tab-pane" id="' . $type . '">";

Example 2: Variable between double quotes (option 1)

If you have a variable that you want to pass in a string you can just put it in there if you use double quotes and de variable is nog 'touching' the other words. It should always have spaces.

$output .= "<p>i would like to $your_text_here with you.</p>";

Example 3: Escaping quotes in a string

Escaping characters in a string can be done by using a \ (backslash) before the character you want to escape.

$output .= "<div class=\"tab-pane\" id=\"example-id\">";

Example 4: Variable between double quotes without spaces next to it

You can place your variable between {} braces if you use double quotes (option 2)

$output .= "<div class=\"tab-pane\" id=\"{$type}\">";

This question was however already answered in Mixing PHP variable with string literal