PHP - Variable inside variable?

$bookA = "123"; $开发者_C百科crack = "A";

I want to do something similar to this:

echo $book$crack;

Such that the output is 123.

What is the correct syntax for the echo command?

Thanks.

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echo ${"book" . $crack};

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These are called variable variables, but you should use arrays instead.

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$varname = 'book'.$crack;
echo $$varname;

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You might want to use an associative array.

For instance:

$book = array();
$book["A"] = "Some Book";
$crack = "A";

//Later
echo $book[$crack];

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This will work:

$bookA = "123";
$crack = "A";
$var = "book$crack";
echo $$var;

---

Try the following:

echo ${book.$crack};

It works for me.