What does if(); do, where the semi-colon is right after the parentheses?

Question

It happens that, when writing some PHP code, I accidentally put a semicolon ; right after an if statement. For example:

if($a > 1);
{
   ....
}

I thought that PHP should raise an error in this case, but it is not. That kind of syntax should have a meaning, I'm just wondering what it is.

For what I could see the condition seems to be always true when the ; is added but I'm not sure at all this is the meaning.

Answer 1

A single ; can be read as an "empty statement" and

if($a > 1);
{
   ....
}

is equivalent to

if($a > 1)
    ;        // execute an empty statement if $a > 1

// then execute the following block of code.
{
   ....
}

For what I could see the condition seems to be always true when the ; is added

It only seems like it since the block is executed regardless of the if-statement.

Answer 2

Adding the semi-colon essentially ends the if block before the braces. It isn't true, it's just that you don't do anything in the if.

Think about it like this, if you don't have braces:

if($a>1)
  echo "Yes";
echo "No";

does everything before the first semi-colon inside the if. So in your case, there is nothing before the first semi-colon, so nothing happens.