# PHP quotes and concatenation style rules for "highest code performance"

<!-- slug: php-quotes-and-concatenation-style-rules-for-highest-code-performance -->

## The problem

PHP has many ways to concatenate strings, and many ways to expand variables inside strings. But which is the fastest?

## The solution

the rule is simple, use double quotes for concatenation and use curly braces for variable expansion.
example:
```php
$var = 'foo';
echo "This is a {$var} notation";
```

for more details, see the [rules](#the-rules) section below and the [tests](#the-tests) section below that.

## The rules

1. Always use double-quoted strings for concatenation, because it's the fastest method. The only exception is when you're concatenating a variable with a literal string that has no variables in it, then you can use single-quoted strings for a tiny bit of extra performance.
2. Put your variables in `"This is a {$variable} notation"`, because it's the fastest method which still allows complex expansions like `"This {$var['foo']} is {$obj->awesome()}!"`. You cannot do that with the `"${var}"` style.
3. Feel free to use single-quoted strings for TOTALLY literal strings such as array keys/values, variable values, etc, since they are a TINY bit faster when you want literal non-parsed strings. But I had to do 1 billion iterations to find a 1.55% measurable difference. So the only real reason I'd consider using single-quoted strings for my literals is for code cleanliness, to make it super clear that the string is literal.
4. If you think another method such as `sprintf()` or `'this'.$var.'style'` is more readable, and you don't care about maximizing performance, then feel free to use whatever concatenation method you prefer!


## The tests

*refer to the source of tests results [here](https://www.php.net/manual/en/language.types.string.php#120160)*