Q: What is
A: Its the scope resolution operator (double colon)
An experienced PHP'er immediately knows what it means. Less experienced (and not Hebrew) developers may want to read this.
Q: What is the cause of this warning: 'Warning: Cannot modify header information - headers already sent', and what is a good practice to prevent it?
A: *Cause:* body data was sent, causing headers to be sent too.
Prevention: Be sure to execute header specific code first before you output any body data. Be sure you haven't accidentally sent out whitespace or any other characters.
Q: What is wrong with this query:
A: 1. It is vulnarable to SQL injection. Never use user input directly in queries. Sanitize it first. Preferebly use prepared statements (PDO) 2. Don't select all columns (*), but specify every single column. This is predominantly ment to prevent queries hogging up memory when for instance a BLOB column is added at some point in the future.
Q: What is wrong with this if statement:
A:
Q: Given this code:
A:
OOP specific
Q: What is the difference between
A:
Q: What is wrong with this code:
Q: What is the difference between an interface and an abstract class?
A: An interface defines a contract between an implementing class is and an object that calls the interface. An abstract class pre-defines certain behaviour for classes that will extend it. To a certain degree this can also be considered a contract, since it garantuees certain methods to exist.
Q: What is wrong with classes that predominantly define getters and setters, that map straight to it's internal members, without actually having methods that execute behaviour?
A: This might be a code smell since the object acts as an ennobled array, without much other use.
Q: Why is PHP's implementation of the use of interfaces sub-optimal?
A: PHP doesn't allow you to define the expected return type of the method's, which essentially renders interfaces pretty useless. :-P
T_PAAMAYIM_NEKUDOTAYIM?A: Its the scope resolution operator (double colon)
An experienced PHP'er immediately knows what it means. Less experienced (and not Hebrew) developers may want to read this.
Q: What is the cause of this warning: 'Warning: Cannot modify header information - headers already sent', and what is a good practice to prevent it?
A: *Cause:* body data was sent, causing headers to be sent too.
Prevention: Be sure to execute header specific code first before you output any body data. Be sure you haven't accidentally sent out whitespace or any other characters.
Q: What is wrong with this query:
"SELECT * FROM table WHERE id = $_POST[ 'id' ]"?A: 1. It is vulnarable to SQL injection. Never use user input directly in queries. Sanitize it first. Preferebly use prepared statements (PDO) 2. Don't select all columns (*), but specify every single column. This is predominantly ment to prevent queries hogging up memory when for instance a BLOB column is added at some point in the future.
Q: What is wrong with this if statement:
if( !strpos( $haystack, $needle ) ...?A:
strpos returns the index position of where it first found the $needle, which could be 0. Since 0 also resolves to false the solution is to use strict comparison: if( false !== strpos( $haystack, $needle )...Q: What is the preferred way to write this if statement, and why?
if( 5 == $someVar ) or if( $someVar == 5 )
A: The former, as it prevents accidental assignment of 5 to $someVar when you forget to use 2 equalsigns ($someVar = 5), and will cause an error, the latter won't. Q: Given this code:
function doSomething( &$arg )
{
$return = $arg;
$arg += 1;
return $return;
}
$a = 3;
$b = doSomething( $a );$a and $b after the function call and why?A:
$a is 4 and $b is 3.
The former because $arg is passed by reference, the latter because the
return value of the function is a copy of (not a reference to) the
initial value of the argument.OOP specific
Q: What is the difference between
public, protected and private in a class definition?A:
public makes a class member available to "everyone", protected makes the class member available to only itself and derived classes, private makes the class member only available to the class itself.Q: What is wrong with this code:
class SomeClass
{
protected $_someMember;
public function __construct()
{
$this->_someMember = 1;
}
public static function getSomethingStatic()
{
return $this->_someMember * 5; // here's the catch
}
}Q: What is the difference between an interface and an abstract class?
A: An interface defines a contract between an implementing class is and an object that calls the interface. An abstract class pre-defines certain behaviour for classes that will extend it. To a certain degree this can also be considered a contract, since it garantuees certain methods to exist.
Q: What is wrong with classes that predominantly define getters and setters, that map straight to it's internal members, without actually having methods that execute behaviour?
A: This might be a code smell since the object acts as an ennobled array, without much other use.
Q: Why is PHP's implementation of the use of interfaces sub-optimal?
A: PHP doesn't allow you to define the expected return type of the method's, which essentially renders interfaces pretty useless. :-P
