PHP - concatenate or directly insert variables in

Question

I am wondering, What is the proper way for inserting PHP variables into a string?

This way:

echo "Welcome ".$name."!"

Or this way:

echo "Welcome $name!"

Both of these methods work in my PHP v5.3.5. The latter is shorter and simpler but I'm not sure if the first is better formatting or accepted as more proper.

Answer 1

Between those two syntaxes, you should really choose the one you prefer :-)

Personally, I would go with your second solution in such a case (Variable interpolation), which I find easier to both write and read.

The result will be the same; and even if there are performance implications, those won't matter ¹.

As a sidenote, so my answer is a bit more complete: the day you'll want to do something like this:

echo "Welcome $names!";

PHP will interpret your code as if you were trying to use the $names variable -- which doesn't exist.

That day, you'll need to use {}:

echo "Welcome {$name}s!"

No need to fallback to concatenations.

Also note that your first syntax:

echo "Welcome ".$name."!";

Could probably be optimized, avoiding concatenations, using:

echo "Welcome ", $name, "!";

(But, as I said earlier, this doesn't matter much...)

_{1 - Unless you are doing hundreds of thousands of concatenations vs interpolations -- and it's probably not quite the case.}

Answer 2

Double-quoted strings are more elegant because you don't have to break up your string every time you need to insert a variable (like you must do with single-quoted strings).

However, if you need to insert the return value of a function, this cannot be inserted into a double-quoted string--even if you surround it with braces!

//syntax error!!
//$s = "Hello {trim($world)}!"

//the only option
$s = "Hello " . trim($world) . "!";

Answer 3

since php4 you can use a string formater:

$num = 5;
$word = 'banana';
$format = 'can you say %d times the word %s';
echo sprintf($format, $num, $word);

Answer 4

It only matter of taste.
Use whatever you wish.

Most of time I am using second one but it depends.

Let me suggest you also to get yourself a good editor which will highlight a variable inside of a string

Answer 5

I know this is an old question, but I think someone has to mention all pros & cons:

Better Syntax: That's personal preference.

Performance: No difference. As many mentioned, double-quote might be faster if using unrealistically many variables.

Better Usage: Single quote (mostly). As @Khez said, with single quote you can concatenate anything, even function calls and variable modification, like so: echo 'hi ' . trim($name) . ($i + 1);. The only thing double-quote can do that single-quote cannot do is usage of \n, \r, \t and alike.

Readability: No difference (may personal preference apply).

Writability/Re-Writability/Debugging: In 1-line statements there is no difference, but when dealing with multiple lines, it's easier to comment/uncomment lines while debugging or writing. For example:

$q = 'SELECT ' .
     't1.col1 ' .
     ',t2.col2 ' .
   //',t3.col3 ' .
     'FROM tbl1 AS t1 ' .
     'LEFT JOIN tbl2 AS t2 ON t2.col2 = t1.col1 ' .
   //'LEFT JOIN tbl3 AS t3 ON t3.col3 = t2.col2 ' .
     'WHERE t1.col1 = ' . $x . ' ' .
     '  AND t2.col2 = ' . $y . ' ' .
   //'  AND t3.col3 = ' . $z . ' ' .
     'ORDER BY t1.col1 ASC ' .
     'LIMIT 10';

Less Escaping: Single-quote. For single quote you need to escape 2 characters only (' and \). For double quote you need to escape 2 characters (", \) and 3 more if required ($, { and }).

Less Changes: Single quote. For example if you have the following code:

echo 'Number ' . $i . '!';

And you need to increment 1 to $i, so it becomes likes:

echo 'Number ' . ($i + 1) . '!';

But for double quote, you will need to change this:

echo "Number $i!";

to this:

echo "Number " . ($i + 1) . "!";

---

Conclusion: Use what you prefer.

Answer 6

You Should choose the first one. They have no difference except the performance the first one will be the fast in the comparison of second one.

If the variable inside the double quote PHP take time to parse variable.

Check out this Single quotes or double quotes for variable concatenation?

This is another example Is there a performance benefit single quote vs double quote in php?

I did not understand why this answer in above link get upvoted and why this answer got downvote.

As I said same thing.

You can look at here as well

What is faster in PHP, single or double quotes?