PHP interview questions and answers

PHP interview questions and answers

1)    What does a special set of tags <?= and ?> do in PHP?

2)    What’s the difference between include and require?

3)    I am trying to assign a variable the value of 0123, but it keeps coming up with a different number, what’s the problem?

4)    Would I use print “$a dollars” or “{$a} dollars” to print out the amount of dollars in this example?

5)    How do you define a constant?

6)    How do you pass a variable by value?

7)    Will comparison of string “10” and integer 11 work in PHP?

8)    When are you supposed to use endif to end the conditional statement?

9)    Explain the ternary conditional operator in PHP?

10) How do I find out the number of parameters passed into function?

11) If the variable $a is equal to 5 and variable $b is equal to character a, what’s the value of $$b?

12) What’s the difference between accessing a class method via -> and via ::?

13) Are objects passed by value or by reference?

14) How do you call a constructor for a parent class?

15) What’s the special meaning of __sleep and __wakeup?

16) Why doesn’t the following code print the newline properly?

17) Would you initialize your strings with single quotes or double quotes?

18) How come the code <?php print “Contents: $arr[1]”; ?> works, but <?php print “Contents: $arr[1][2]”; ?> doesn’t for two-dimensional array of mine?

19) What is the difference between characters 23 and x23?

20) With a heredoc syntax, do I get variable substitution inside the heredoc contents?

 

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PHP FAQ

PHP FAQ

  1. What does a special set of tags <?= and ?> do in PHP?
    – The output is displayed directly to the browser.
  2. What’s the difference between include and require?
    – It’s how they handle failures. If the file is not found by require(), it will cause a fatal error and halt the execution of the script. If the file is not found by include(), a warning will be issued, but execution will continue.
  3. I am trying to assign a variable the value of 0123, but it keeps coming up with a different number, what’s the problem?
    – PHP Interpreter treats numbers beginning with 0 as octal. Look at the similar PHP interview questions for more numeric problems.
  4. Would I use print “$a dollars” or “{$a} dollars” to print out the amount of dollars in this example?
    – In this example it wouldn’t matter, since the variable is all by itself, but if you were to print something like “{$a},000,000 mln dollars”, then you definitely need to use the braces.
  5. How do you define a constant?
    – Via define() directive, like define (“MYCONSTANT”, 100);
  6. How do you pass a variable by value?
    – Just like in C++, put an ampersand in front of it, like $a = &$b
  7. Will comparison of string “10″ and integer 11 work in PHP? – Yes, internally PHP will cast everything to the integer type, so numbers 10 and 11 will be compared.
  8. When are you supposed to use endif to end the conditional statement?
    – When the original if was followed by : and then the code block without braces.
  9. Explain the ternary conditional operator in PHP?
    – Expression preceding the ? is evaluated, if it’s true, then the expression preceding the : is executed, otherwise, the expression following : is executed.
  10. How do I find out the number of parameters passed into function?
    – func_num_args() function returns the number of parameters passed in.
  11. If the variable $a is equal to 5 and variable $b is equal to character a, what’s the value of $$b?
    – 100, it’s a reference to existing variable.
  12. What’s the difference between accessing a class method via -> and via ::?
    – :: is allowed to access methods that can perform static operations, i.e. those, which do not require object initialization.
  13. Are objects passed by value or by reference?
    – Everything is passed by value.
  14. How do you call a constructor for a parent class?
    – parent::constructor($value)
  15. What’s the special meaning of __sleep and __wakeup?
    – __sleep returns the array of all the variables than need to be saved, while __wakeup retrieves them.
  16. Why doesn’t the following code print the newline properly? <?php
    $str = ‘Hello, there.nHow are you?nThanks for visiting TechInterviews’;
    print $str;
    ?>
    Because inside the single quotes the n character is not interpreted as newline, just as a sequence of two characters – and n.
  17. Would you initialize your strings with single quotes or double quotes?
    – Since the data inside the single-quoted string is not parsed for variable substitution, it’s always a better idea speed-wise to initialize a string with single quotes, unless you specifically need variable substitution.
  18. How come the code <?php print “Contents: $arr[1]“; ?> works, but <?php print “Contents: $arr[1][2]“; ?> doesn’t for two-dimensional array of mine?
    – Any time you have an array with more than one dimension, complex parsing syntax is required. print “Contents: {$arr[1][2]}” would’ve worked.
  19. What is the difference between characters �23 and x23?
    – The first one is octal 23, the second is hex 23.
  20. With a heredoc syntax, do I get variable substitution inside the heredoc contents?
    – Yes.