function select($select = '*')
{
if( is_string($select) ) {
$select = explode(',', $select) ;
}
foreach($select as $s) {
$s = trim($s) ;
if($s != '') {
$this->aSelect[] = $s ;
}
}
return $this ;
}
In PHP, what is meant by return $this.
3
There are many scenarios in which one might want to return $this from a function, but the most popular one is ‘method chaining’.
For example, in an SQL abstraction layer, you may have an object that represents a query, and then call a series of methods on it to extend it. Consider the following code:
$query = $database->select();
$query->from('users');
$query->whereEquals('username', $username);
$query->orderBy('username');
$query->limit(1);
$user = $query->executeSingleRow();
If each of $query‘s methods returns the modified query object, we can instead write this as:
$user = $database
->select()
->from('users')
->whereEquals('username', $username)
->orderBy('username')
->limit(1)
->executeSingleRow();
The second version is closer to how you’d write an actual SQL query, and it works without introducing the exta $query variable.
By returning $this you it makes it easier for the programmer to chain commands. Consider a car object. You could say $car->start()->forward()->left()->forward() on line if you return $this in each function.
There is actually a question about this in stack overflow which could help clarify what method chaining is: https://stackoverflow.com/questions/3724112/php-method-chaining
Chian type programming…
return $this will return a same object all the time. that make you be ready to call upon it a next function, next function again return same instance such that to call upon it a third function and so on.
see example first
class MY_CLASS(){
string attrib;
func SetMethod(string value){this.attrib=value;}
}
to call Method1 on un-known object, we can write as following.
(new MY_CLASS()).Method1
expend above class
class MY_CLASS(){
string attrib;
func SetMethod(string value){this.attrib=value;}
func int GetMethod(){return this.Attrib);}
}
Now to call it for GetMethod we can’t do with un-known object as following
new MY_CLASS().SetMethod(30);
a = new My_CLASS().GetMethod();
Yah in other languages like C# we can do as following
a=(new MY_CLASS().SetMethod(30)).GetMethod();
to achieve same facilities in php you need to write ‘return $this’ in function where you think to be use for consegative calls
Hope answer is clear.