//In PHP,
$a ? $b : echo $c //does not work but
$a ? $b : print $c //works
Is there a reason for this?
BTW,is not a keyword in PHP?
views:
227answers:
6
A:
return value. if you wrote
$x = $a?$b:echo $c;
what value would $x get on $a being false?
print always returns 1. echo doesn't return anything.
SF.
2010-03-10 09:45:09
But I don't have the `$x =` part .Also I tried a function that doesn't have a return value,still works.
2010-03-10 09:45:58
PHP functions that do not explicitly return a value will be 'void', that is, they return 'null'. echo, not being a function but a language construct, doesn't return even that. As for lack of $x = ..., PHP is an interpreter. It first calculates the value of the ?: expression, and only then decides whether to discard it or pass it.
SF.
2010-03-10 09:52:42
Could whoever modded my answer down explain what is wrong about it?
SF.
2010-03-10 09:59:55
+1
A:
echo does not have a return value, print does!
void echo ( string $arg1 [, string $... ] )
int print ( string $arg )
from php.net
This matters in this case since the ternary operator expects expressions
(expr1) ? (expr2) : (expr3)
echo "something" cannot be classified as an expression.
not is not a PHP keyword.
Wesho
2010-03-10 09:47:40
+2
A:
echo is not a function, it's language construct. It does not return anything. Another void functions always "return" NULL. It's why the compiler throws error unexpected T_ECHO.
printf, however, is a function and always returns 1.
For example this will work:
function echo2($e)
{
echo($e);
}
$a ? $b : echo2('foo');
Petr Peller
2010-03-10 09:50:21
Actually, print is a language construct too, but it behaves like a function.
SF.
2010-03-10 09:58:04
@stereofrog: so official documentation of PHP (first result in the search) is not an authoritative source on information about whether PHP contains such a thing as "language constructs"?
SF.
2010-03-10 15:41:16
A:
Is it because echo is a language construct and print is a function?
majelbstoat
2010-03-10 09:51:29
A:
In c-alike languages there is a difference between statements (like "if", "while" etc) and operators (like +, -, casts etc). Unlike operators, statements cannot be used in expressions, for example, "10 + (if(1) 3 else 4)" is invalid. In php, "echo" is a statement, and "print" is an operator (don't ask). That's why $a = 10 + print 20 is possible, but not $a = 10 + echo 20
stereofrog
2010-03-10 10:11:04