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Possible Duplicate:
Difference between single quote and double quote string in php

Can you use " and ' interchangeably, 100%? Or is there a reason or use for each? What is the difference exactly?

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rockstardev
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2 Answers2

2

Observe for yourself:

$name = 'John';
echo "Hello $name" . '<br>';
echo 'Hello $name';

Result:

Hello John   // result from double quotes
Hello $name  // result from single quotes

As can be seen variables inside double quotes are parsed while in single quotes they aren't.

So when you put variables inside double quotes, they can be parsed and their correct value is output whereas with single quotes, variables are not parsed and you get the same output of variable name itself as in Hello $name.

Since variables inside single quotes aren't parsed, using them is just a little good when it comes to performance.

If there is no question of variables inside quotes, you can use them inter-changeably though keeping above performance tip in mind.

For more information, you can look at the official documentation.

Sarfraz
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  • This also goes for escape sequences like `\r` and `\n`, they won't be parsed in single quotes either. The [manual page on strings](http://php.net/manual/en/language.types.string.php) has more detailed information on the subject. – Another Code Mar 10 '12 at 11:46
  • @AnotherCode: Agreed, I forgot about them, will update the answer for the official link. – Sarfraz Mar 10 '12 at 11:52
1

Just to add to the great answer of Sarfraz, there are certain situations where you would want to use one or the other.

Single quotes ('') are always parsed slightly (minutely) faster than double quotes so if you are an optimization freak, a good rule of thumb is to use single quotes instead of double quotes if you will not be parsing any variables.

However, if you have tons of variables and don't want to do something like:

echo 'My name is ' . $name . '!';

then you're better off with double quotes.

However when dealing with html output, you may consider the hassle of escaping your double quotes too tedious to deal with:

echo "<p id=\"myParagraph\">$name</p>";

So in this case the vote goes to single quotes.

Another thing is that when you build SQL queries with PHP, you may notice that you might prefer using double quotes to be able to parse variables and avoid escaping the single quotes:

"SELECT * FROM CoolGuys WHERE Name = '$name'";

In the end it's all a matter of preferrence. :)

Good luck!

jdalangin
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