Not getting the specific output without braces [closed]

Answer 1

You can re-write the expression like this to see the sequence of evaluations: ((("$x+$y=".$x) + $y)."
");

Here is what happens in detail:

1. The string is interpolated takes place changing "$x+$y=" to "10+7="
2. The string concatenation takes place "10+7=".$x leading to "10+7=10"
3. The addition between a string and a number takes place "10+7=10"+$y evaluates to "10+7" and eventually "17" because php attempts to convert the string into a number. During this process it starts at the left side of the string and in your example it finds 10. Next the + symbol is found, which is not a number and this terminates the attempt to convert the string into a number. However, what has been found to be a number (10) remains as the numeric interpretation of the string.
4. 17 is concatenated with the last string
and this is echoed out.

Hope that helps, Loddi