PHP echo does not work

I am trying to print a variable between curly braces as

开发者_如何学Python

Product_number{product_version}

I tried

echo "$product_number{$product_version}";

But that does not work. I don't understand why :(

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try using double braces:

echo "$product_number{{$product_version}}";

You can also do:

echo "$product_number{".$product_version."}";

{ followed by $ is treated specially. It is mainly used when you want to append a string immediately at the end of a variable's value:

$v = 'hack';
echo "I {$v}ed it";

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echo $product_number . "{" . $product_version . "}";

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Escape the "{":

echo "$product_number\{$product_version}";