PHP - concatenate or directly insert variables in string

Question

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. - note that it will only work if you use "" not '' for your string.

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.}

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) . "!";

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);

Source: sprintf()

I prefer this all the time and found it much easier.

echo "Welcome {$name}!"

From the point of view of making thinks simple, readable, consistent and easy to understand (since performance doesn't matter here):

• Using embedded vars in double quotes can lead to complex and confusing situations when you want to embed object properties, multidimentional arrays etc. That is, generally when reading embedded vars, you cannot be instantly 100% sure of the final behavior of what you are reading.

• You frequently need add crutches such as {} and \, which IMO adds confusion and makes concatenation readability nearly equivalent, if not better.

• As soon as you need to wrap a function call around the var, for example htmlspecialchars($var), you have to switch to concatenation.

• AFAIK, you cannot embed constants.

In some specific cases, "double quotes with vars embedding" can be useful, but generally speaking, I would go for concatenation (using single or double quotes when convenient)

I know this question already has a chosen answer, but I found this article that evidently shows that string interpolation works faster than concatenation. It might be helpful for those who are still in doubt.