The difference between using single quotes and double quotes as string delimiters in JavaScript/PHP

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I like to keep all my string delimiters in languages such as PHP and JavaScript consistent. I consistently use single quotes for a couple of good reasons, so when I encounter someone else’s script that uses double quotes the OCD in me makes me change them all to single quotes…but that is a different problem.

If you’re coming from a language such as C# or Java then note that in PHP and JavaScript there is no such thing as a character datatype – as such, you can use either single or double quotes to delimit strings.

If I could only give you one reason why I consistently use single quotes then I would have to go with this:

If you ever (God forbid) need to write HTML in a string, you don’t need to escape the double quotes around attribute values. Instead of:

    "<div id=\"foo\" class=\"bar\">foobar</div>"

You write:

    '<div id="foo" class="bar">foobar</div>'

…which is lots less characters to type and I’d say more readable. Also, I more frequently use double quotes in my JavaScript/PHP strings than single quotes so it really does make sense.

The other reason is that if you use double quotes, PHP will actually parse the contents of the string to find variables and escape characters (\n, \r, \t etc.) which it’ll replace with the variable value or correct escape character respectively. So for example:

<?php

    $baz = 'bar';
    echo "foo\n$baz";

?>

Will print:

foo
bar

Whereas:

<?php

    $baz = 'bar';
    echo 'foo\n$baz';

?>

Will print:

foo\n$baz

So if you don’t need any of this functionality in your string, you’re making PHP do some extra work for no reason.

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