Technical Interview Questions

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.
   
   

1. 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.
   
   
2. 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.
   
   
3. Are objects passed by value or by reference? - Everything is passed by value.
   
   
4. How do you call a constructor for a parent class? - parent::constructor($value)
   
   

1. I want to combine two variables together:

 $var1 = ‘Welcome to ‘;

 $var2 = ‘TechInterviews.com’;

What will work faster? Code sample 1:

$var 3 = $var1.$var2;

Or code sample 2:

$var3 = "$var1$var2";

Both examples would provide the same result - $var3 equal to “Welcome to TechInterviews.com”. However, Code Sample 1 will work significantly faster. Try it out with large sets of data (or via concatenating small sets a million times or so), and you will see that concatenation works significantly faster than variable substitution.

1. What’s relationship between JavaScript and ECMAScript? - ECMAScript is yet another name for JavaScript (other names include LiveScript). The current JavaScript that you see supported in browsers is ECMAScript revision 3.
2. What are JavaScript types? - Number, String, Boolean, Function, Object, Null, Undefined.
3. How do you convert numbers between different bases in JavaScript? - Use the parseInt() function, that takes a string as the first parameter, and the base as a second parameter. So to convert hexadecimal 3F to decimal, use parseInt (”3F”, 16);
4. What does isNaN function do? - Return true if the argument is not a number.

1. On a fresh install, why does Apache have three config files - srm.conf, access.conf and httpd.conf?
The first two are remnants from the NCSA times, and generally you should be ok if you delete the first two, and stick with httpd.conf.
2. What’s the command to stop Apache? - kill the specific process that httpd is running under, or killall httpd. If you have apachectl installed, use apachectl stop.
3. What does apachectl graceful do? - It sends a SIGUSR1 for a restart, and starts the apache server if it’s not running.
4. How do you check for the httpd.conf consistency and any errors in it? - apachectl configtest