Tricky PHP Interview Questions & Answers on “While Loops – 2”.
1. What will be the output of the following PHP code?
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$i = 0;
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while($i = 10)
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{ -
print "hi";
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} -
print "hello";
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?>
a) hello
b) infinite loop
c) hihello
d) error
Answer: b
Clarification: While condition always gives 1.
2. What will be the output of the following PHP code?
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$i = "";
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while ($i = 10)
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{ -
print "hi";
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} -
print "hello";
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?>
a) hello
b) infinite loop
c) hihello
d) error
Answer: b
Clarification: While condition always gives 1.
3. What will be the output of the following PHP code?
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$i = 5;
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while (--$i > 0)
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{ -
$i++; print $i; print "hello";
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} -
?>
a) 4hello4hello4hello4hello4hello…..infinite
b) 5hello5hello5hello5hello5hello…..infinite
c) no output
d) error
Answer: b
Clarification: i is decremented in the while loop in the condition check and then incremented back.
4. What will be the output of the following PHP code?
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$i = 5;
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while (--$i > 0 && ++$i)
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{ -
print $i;
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} -
?>
a) 5
b) 555555555…infinitely
c) 54321
d) error
Answer: b
Clarification: As it is && operator it is being incremented and decremented continuously.
5. What will be the output of the following PHP code?
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$i = 5;
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while (--$i > 0 || ++$i)
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{ -
print $i;
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} -
?>
a) 54321111111….infinitely
b) 555555555…infinitely
c) 54321
d) 5
Answer: a
Clarification: As it is || operator the second expression is not evaluated till i becomes 1 then it goes into a loop.
6. What will be the output of the following PHP code?
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$i = 0;
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while(++$i || --$i)
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{ -
print $i;
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} -
?>
a) 1234567891011121314….infinitely
b) 01234567891011121314…infinitely
c) 1
d) 0
Answer: a
Clarification: As it is || operator the second expression is not evaluated and i is always incremented, in the first case to 1.
7. What will be the output of the following PHP code?
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$i = 0;
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while (++$i && --$i)
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{ -
print $i;
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} -
?>
a) 1234567891011121314….infinitely
b) 01234567891011121314…infinitely
c) no output
d) error
Answer: c
Clarification: The first condition itself fails thus the loop exists.
8. What will be the output of the following PHP code?
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$i = 0;
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while ((--$i > ++$i) - 1)
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{ -
print $i;
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} -
?>
a) 00000000000000000000….infinitely
b) -1-1-1-1-1-1-1-1-1-1…infinitely
c) no output
d) error
Answer: a
Clarification: (–$i > ++$i) evaluates to 0 but -1 makes it enters the loop and prints i.
9. What will be the output of the following PHP code?
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$i = 2;
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while (++$i)
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{ -
while ($i --> 0)
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print $i;
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} -
?>
a) 210
b) 10
c) no output
d) infinite loop
Answer: a
Clarification: The loop ends when i becomes 0.
10. What will be the output of the following PHP code?
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$i = 2;
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while (++$i)
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{ -
while (--$i > 0)
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print $i;
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} -
?>
a) 210
b) 10
c) no output
d) infinite loop
Answer: d
Clarification: The loop never ends as i is always incremented and then decremented.
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