Listed arrow notations in php?

Question

This is something that I have been really curious about. I have tried to find the answer myself but I can't exactly think what to google. So first off, I am used to doing a regular query method either like this (when escaping):

$Database->query($sql)

or if using prepared statements like this:

$Database->statement($sql, array('ss', $val1, $val2))

However when reading through the source code of a project, I found this:

$id = DB::SQL()
                ->select("postId")
                ->from("post")
                ->where("conversationId=:conversationId")->bind(":conversationId", $conversation["conversationId"])
                ->orderBy("time DESC")
                ->limit(1)
                ->exec()
                ->result();

Now I know this is PDO, and also a random example however since I read this I've been wondering how this is done. If someone would be kind enough to explain then I'd really appreciate it.

Are you asking how "method chaining" is implemented? Simple, have each method return the same object it was called with. If it's part of a class, then `return $this;`. — gen_Eric, Oct 16 '14 at 17:10
PDO in PHP does not support method chaining, nor does the given example look like PHP's PDO interface — dbf, Oct 16 '14 at 17:50

score 1 · Accepted Answer · edited May 23 '17 at 12:05

The method you have done here is method chaining.

A simple example from here.

<?php

class fakeString

{
private $str;
function __construct()
{
    $this->str = "";
}

function addA()
{
    $this->str .= "a";
    return $this;
}

function addB()
{
    $this->str .= "b";
    return $this;
}

function getStr()
{
    return $this->str;
}
}


$a = new fakeString();

echo $a->addA()->addB()->getStr(); //outputs ab

Listed arrow notations in php?

1 Answers1