I have one variable:
$a = 5;
Let’s do the math below:
$a++ + $a- + -$a + ++$a + $a++ + ++$a - $a- + $a
With the help of the PHP language, I calculated the result as 22. But I don’t know why it got this result? Hope for a help!
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Answer
Points to consider
- $a++ : First $a value will be used in expression and then incremented.
$a = 5; echo $a++; // Will print 5 only, as $a is used first and then incremented. echo $a; // will print 6 as it is incremented in previous expression.
- ++$a : First value is incremented and then incremented value of $a will be used in expressions.
$a = 5; echo ++$a; // Will print 6 as value is incremented first and then used in expression.
- -$a : simple negation of any value
$a = 5; $b = -6; echo -$a; // -5 echo -$b; // 6
- Last but not least, $a-, it is
-(minus)operator after$a, you can add space after it. But things turn out when another operator plus or minus is used b/w operands i.e.$a- + $b, you can say it does the operator multiplication.
-(minus) -(minus) ==> +(plus) -(minus) +(plus) ==> -(minus) +(plus) -(minus) ==> -(minus) +(plus) +(plus) ==> +(plus) e.g. $a = 5 ; $b = 10; echo $a - - $b; // $a + $b = 15 echo $a - + $b; // $a - $b = -5 echo $a + - $b; // $a - $b = -5 echo $a + + $b; // $a + $b = 15
Now coming to your question
$a++ + $a- + -$a + ++$a + $a++ + ++$a - $a- + $a; ==> simplify it with operator multiplication ($a++) + $a - (-$a) + (++$a) + ($a++) + (++$a) - $a - $a; 5 + 6 - (-6) + (7) + 7 + 9 - 9 - 9; // 22 (post +1) (pre +1) (post +1) (pre +1)