What does { } do within a string?

Question

$name = "jason";
$p = "hello-{hello2}-$name-{$name}";
echo $p;

output :

hello-{hello2}-jason-jason

Came across some examples of prepared statements and noticed this. If its encompassing a variable, it removes them, otherwise it keeps them. Why is this behavior necessary when

echo "$name";

gets you the same result as

echo "{$name}";

or is it just readability?

Answer 1

It's used as a delimiter for variables in strings. This is necessary in some cases, as PHP's string parser isn't Greedy aand will mis-interpret many common structs.

e.g.

$foo = array();
$foo['bar'] = array();
$foo['bar']['baz'] = 'qux';

echo "Hello $foo[bar][baz]";

will actually print

Hello Array[baz]

Because it's parsed as

echo "Hello ", $foo['bar'], "[baz]";
        ^          ^           ^
      string     array       string

Using {} forces PHP to consider the array reference as single entity:

echo "Hello, {$foo['bar']['baz']}";  // prints "Hello, qux"

It also helps differentiate ambiguous stuff

$foo = 'bar';

echo "$foos" // undefined variable 'foos'
echo "{$foo}s" // variable containing 'bar' + string 's'