PHP Interview Questions and Answers

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.

Yes, internally PHP will cast everything to the integer type, so numbers 10 and 11 will be compared.

Everything is passed by value.

__sleep returns the array of all the variables than need to be saved, while __wakeup retrieves them.

htmlspecialchars only takes care of <, >, single quote ', double quote " and ampersand. htmlentities translates all occurrences of character sequences that have different meaning in HTML.

^^

PHP Interpreter treats numbers beginning with 0 as octal.

func_num_args() function returns the number of parameters passed in.

100, it's a reference to existing variable.

:: is allowed to access methods that can perform static operations, i.e. those, which do not require object initialization.

Any time you have an array with more than one dimension, complex parsing syntax is required. print "Contents: {$arr[1][2]}" would've worked.

Yes.

On large strings that need to be formatted according to some length specifications, use wordwrap() or chunk_split().

The major difference is the length of the hash generated. CRC32 is, evidently, 32 bits, while sha1() returns a 128 bit value, and md5() returns a 160 bit value. This is important when avoiding collisions.

Crypto usage in PHP is simple, but that doesn't mean it's free. First off, depending on the data that you're encrypting, you might have reasons to store a 32-bit value in the database instead of the 160-bit value to save on space. Second, the more secure the crypto is, the longer is the computation time to deliver the hash value. A high volume site might be significantly slowed down, if frequent md5() generation is required.