//1.
if(condition)
    $variable = true;
else
    $variable = false;

//or...

//2.
if(condition)
{
    $variable = true;
}
else
{
    $variable = false;
}

//3.
if(condition) $variable = true;
else $variable = false;

//4.
if(condition) {
    $variable = true;
}
else {
    $variable = false;
}

//which do you like best? 1, 2, 3 or 4?