php, infinite loop in while() loop

Question

/// infinite loop??
$x=1; 
while($x=9){ 
echo $x;
$x++;
}

i dont understand the reason behind, why the above code causes infinite loop in my opinio

Answer 1

$x=9 is an assignment, and is always true. Perhaps you meant $x==9, or some other relational operator.

Answer 2

You are assigning the value of 9 to the variable x instead of performing a relational comparison. A common mistake. = is the assignment operator whereas == is the equality comparison operator.

http://en.wikipedia.org/wiki/Assignment_(computer_science)#Assignment_versus_equality

Answer 3

You mean

$x == 9

But in your example it won't do anything, because $x != 9. You probably mean

while($x < 9)