What will be the output of the following PHP code?

Question

What will be the output of the following PHP code? <?php$i = 0;while ($i = 10){ print "hi";}print "hello";?>

BlackTom AI · Accepted Answer

The while condition uses assignment (=) instead of comparison, so each evaluation sets $i to 10 and the assigned value (10) is treated as true — causing the loop to never terminate.

1. Relevant knowledge points and concepts
- In PHP an assignment expression (e.g., $i = 10) returns the assigned value.  
- Nonzero integers are truthy in PHP; 0 is falsey.  
- while(condition) repeats as long as condition evaluates to true.  
- Using = in a condition is legal PHP (no syntax error), though often a logic bug.

2. Step-by-step reasoning
- Line 1: $i = 0; initializes $i to 0.  
- while ($i = 10) is evaluated for the first time:
  - The assignment operator sets $i to 10.
  - The expression ($i = 10) evaluates to the integer 10.
  - PHP treats 10 as boolean true, so the while body executes.
- Inside the loop print "hi"; $i is 10 and is not changed inside the loop.
- Loop iteration ends; condition is checked again: ($i = 10) reassigns 10 to $i (no change), expression again yields 10 → true.
- The loop repeats indefinitely, printing "hi" forever. The program never reaches print "hello".

3. Intermediate values shown
- Initially: $i = 0
- After first condition evaluation: $i becomes 10, condition value = 10 (truthy)
- After each subsequent check: $i remains 10, condition value = 10

4. Why the correct answer is correct
Because the condition always evaluates to a truthy value (10) due to assignment, the loop never exits and "hi" is printed repeatedly forever — an infinite loop.

5. Why other options are incorrect
- a. error: No syntax/runtime error occurs; assignment in condition is valid.  
- b. hello: "hello" would print only after the loop ends; the loop never ends.  
- d. hihello: That would require the loop to terminate after printing hi once; it does not.

6. Conclusion
The code produces an infinite loop, so the correct answer is c. infinite loop.

What will be the output of the following PHP code? <?php$i = 0;while ($i = 10){ print "hi";}print "hello";?>单项选择题

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