在PHP中传递给echo的参数

Question

here are i am providing some examples of echo

Example 1

echo 'The sum is ', 1 + 2; //works fine

Example 2

$x=true;
echo '$x is undefined value ' , ($x===true) ? 'NO' : 'Yes'; //Works fine

Example 3

function f($arg){
  return $arg;
}

echo 'hello ' , f('buddy'); //Works fine

Example 4 -

echo 'hello ' , if($a) { return "wowo"; } else { return "fine"; }; // generate parse error

Here is the point that all example working fine but example 4 its generating parse error.

my questions is that -
1. language constructs can be used for echo arguments ?
2. If yes language constructs can be used, how can we use language constructs for echo arguments ?
3. Only functions that return strings can be passed to echo arguments ?

Answer 1

Yes you can use language constructs to echo arguments or return values. If else is a conditional statement which can be use to evaluate a value. using this you will be able to break the the logic into several pieces and evaluate the condition. the echo will work separately for an each statement. But if you return a value , it will be returned from function and not from the statement. EX:

$value = "hello";
if($a) { $value.= "wowo"; } else { $value.= "fine"; }
echo $value;

in the other hand ternary operator is an operator that takes three arguments and performs an operation .