PHP Multiple Choice Questions on “Operators – 1”.
1. What will be the output of the following PHP code?
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$a = 10;
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echo ++$a;
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echo $a++;
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echo $a;
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echo ++$a;
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?>
a) 11111213
b) 11121213
c) 11111212
d) 11111112
Answer: a
Clarification: ++$a increments a and then prints it, $a++ prints and then increments.
2. What will be the output of the following PHP code?
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$a = 12;
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--$a;
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echo $a++;
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?>
a) 11
b) 12
c) 10
d) error
Answer: a
Clarification: The + operator does union of arrays in that order, then the === operator compares key and value pairs.
3. What will be the output of the following PHP code?
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$x = "test";
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$y = "this";
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$z = "also";
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$x .= $y .= $z ;
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echo $x;
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echo $y;
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?>
a) testthisthisalso
b) testthis
c) testthisalsothisalso
d) error at line 4
Answer: c
Clarification: The x .= y is a shorthand for x = x.y and this is evaluated from right to left.
4. What will be the output of the following PHP code?
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$x = 1;
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$y = 2;
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if (++$x == $y++)
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{ -
echo "true ", $y, $x;
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} -
?>
a) no output
b) true 23
c) true 22
d) true 33
Answer: b
Clarification: x is preincremented and y is post incremented thus both are 2 in the if condition, later y is increment.
5. What will be the output of the following PHP code?
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$y = 2;
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$w = 4;
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$y *= $w /= $y;
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echo $y, $w;
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?>
a) 80.5
b) 44
c) 82
d) 42
Answer: d
Clarification: Expression is evaluated from right to left.
6. What will be the output of the following PHP code?
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$y = 2;
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if ($y-- == ++$y)
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{ -
echo $y;
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} -
?>
a) 2
b) 1
c) 3
d) no output
Answer: a
Clarification: First $y = 2 is compared to and then decremented, then incremented and compared to $y = 2.
7. What will be the output of the following PHP code?
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$y = 2;
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if (**$y == 4)
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{ -
echo $y;
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} -
?>
a) 4
b) 2
c) error at line2
d) no output
Answer: c
Clarification: The ** is not a valid operator, only ++ and — exist.
8. What will be the output of the following PHP code?
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$y = 2;
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if (--$y == 2 || $y xor --$y)
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{ -
echo $y;
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} -
?>
a) 1
b) 0
c) 2
d) no output
Answer: b
Clarification: –$y == 2 is false but y is decremented, the xor gives true if only one of the operands are true, thus 1 xor 0 is true.
9. What will be the output of the following PHP code?
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$y = 2;
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if (--$y <> ($y != $y++))
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{ -
echo $y;
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} -
?>
a) 1
b) 0
c) 2
d) no output
Answer: b
Clarification: –$y == 2 is false but y is decremented, the xor gives true if only one of the operands are true, thus 1 xor 0 is true.
10. What will be the output of the following PHP code?
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echo $x-- != ++$x;
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?>
a) 1
b) 0
c) error
d) no output
Answer: a
Clarification: Automatically x is declared and initialized to 0, then decremented and compared with its increments, thus returns 1.
11. What will be the output of the following PHP code?
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$auth = 1;
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$status = 1;
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if ($result = (($auth == 1) && ($status != 0)))
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{ -
print "result is $result
"; -
} -
?>
a) result is true
b) result is 1
c) error
d) no output
Answer: b
Clarification: Result is x&&y which returns 1 if both x and y are true.