php得到了干扰，并认为1不等于1

Question

I have a variable which value is supposed to be 'age'. I checked if the value of this variable is equal or not to 'age'. Result is not equal.

echo $this->param;  // returns 'age'

if('age' == $this->param) echo 'equal';  // returns false

It inputs only the text 'age'. Where is 'equal'?

What is going on?