Custom PDO fetch function that works in a while loop

Question

If this works..

$stmt = DB::$db->query('SELECT * FROM users');
while ($r = $stmt->fetch()) { print_r($r); }

Is there any way possible to get something like this to work?

function fetch() {
    $stmt = DB::$db->query('SELECT * FROM users');
    return $stmt->fetch();
}
while ($r = fetch()) { print_r($r); }

UPDATE

Or maybe if it's in a class it can work by using some sort of class iterator extension/implementation?

class User {
    public static function fetch() {
        $stmt = DB::$db->query('SELECT * FROM users');
        return $stmt->fetch();
    }
}
while ($r = User::fetch()) { print_r($r); }

SOLUTION

Well I did end up finding a working solution, but the accepted answer which uses a generator is probably the better way to go.

class User {
    private static $stmt;
    public static function fetch() {
        if (static::$stmt === null) {
            static::$stmt = DB::$db->query('SELECT * FROM users');
        }
        return static::$stmt->fetch();
    }
}
while ($r = User::fetch()) { print_r($r); }

I'm sure it is which is why I said I'd recommend the accepted answer over that solution — Rick
– Rick, Commented Mar 7, 2018 at 14:29

IncredibleHat · Accepted Answer · 2018-03-06 18:45:17Z

4

This would do it:

function fetch() {
    $stmt = DB::$db->query('SELECT * FROM users');
    while($row = $stmt->fetch()) { yield $row; }
}
foreach (fetch() as $r) { print_r($r); }

Notes:

It will only do the query once.
The yield is php 5.5+.
Use a foreach on your fetch() mini function.

The reason your initial attempt would not work, is the action just keeps looping indefinitely. Each call to your original fetch() its doing the query each call, and thus returning the first result. This will make the while just go on and on.

edited Mar 6, 2018 at 18:45

answered Mar 6, 2018 at 18:15

IncredibleHat

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8 Comments

Syscall Over a year ago

Good example of generators!

Rick Over a year ago

I was really hoping to get it working with a while loop ran outside of the function. If I use a foreach then even this will work function fetch() { return DB::$db->query('SELECT * FROM users'); }

Your Common Sense Over a year ago

@Rick this answer DOES show you how to use while outside of the function

Rick Over a year ago

Well the title does say "in while loop".. Sorry if that was confusing.. I'm also updating the question by adding a version that uses a class. Perhaps some sort of class iterator extension/implementation can be used to make it work..

IncredibleHat Over a year ago

Oh well. I thought it actually is better to use the while and the generator, instead of just return it all. Despite the foreach. But... PDO, and all that. Its already pretty optimized.

|

Your Common Sense · Accepted Answer · 2018-03-06 18:31:33Z

2

if you don't mid foreach instead of while

function fetch() {
    return DB::$db->query('SELECT * FROM users');
}
foreach (fetch() as $r) { print_r($r); }

answered Mar 6, 2018 at 18:31

Your Common Sense

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1 Comment

IncredibleHat Over a year ago

This is just simply elegant.

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