PHP PDO ALlowed Memory Exhausted when allocating 64 bytes

Question

I have 2 scripts which are technically the same, but one works, and the other produces the error:

( ! ) Fatal error: Allowed memory size of 268435456 bytes exhausted (tried to allocate 64 bytes) in C:\wamp\www\SOTag\SOTag.php on line 29

Line 29 being:

$rows[] = $r;

This is the code that works:

$this->connect_db();
$statement = $this->db_connection->prepare("SELECT * FROM tags WHERE tag LIKE :keywords");
$statement->bindParam(':keywords', $keywords, PDO::PARAM_INT);
$statement->execute(compact('keywords'));

$rows = array();
while($r = $statement->fetch(PDO::FETCH_ASSOC)) {
    $rows[] = $r;
}
return json_encode($rows);

And this is what I need to do (as I need to check for results) but it fails:

$this->connect_db();
$statement = $this->db_connection->prepare("SELECT * FROM tags WHERE tag LIKE :keywords");
$statement->bindParam(':keywords', $keywords, PDO::PARAM_INT);
$statement->execute(compact('keywords'));
$result = $statement->fetch(PDO::FETCH_ASSOC);

$rows = array();
while($r = $result) {
    $rows[] = $r;
}
return json_encode($rows);

why are you using `while($r = while($r = $statement->fetch(PDO::FETCH_ASSOC)) {` ? — NullPoiиteя, Aug 12 '13 at 09:20
How many rows are being returned? What's the memory limit on your PHP install? I have a feeling you're returning too much data to hold in the amount of memory allowed — Bojangles, Aug 12 '13 at 09:22
There is 1 row being returned, this is a tiny script, it's just running on my local machine on localhost with the standard settings — Adam, Aug 12 '13 at 09:22
@YourCommonSense Fair enough. The OP having not demonstrated any debugging attempt, I didn't read further. — RandomSeed, Aug 12 '13 at 09:25

score 2 · Answer 1 · answered Aug 12 '13 at 09:22

2

You've created an infinite loop:

$rows = array();
while($r = $result) {
    $rows[] = $r;
}

PHP is just preventing you from crashing the whole server.

answered Aug 12 '13 at 09:22

Álvaro González

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This answer saved me hours of debugging. – Interface Unknown Sep 09 '18 at 14:58

score 1 · Answer 2 · answered Aug 12 '13 at 09:23

1

while($r = $result) { is the problem.

$result is always evaluated as true, so the loop never stop.

You have to do this:

while($r = $statement->fetch(PDO::FETCH_ASSOC)) {

answered Aug 12 '13 at 09:23

xdazz

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Ok, so I suppose I need to ask, how do I check for results without executing the query twice? – Adam Aug 12 '13 at 09:24
@Adam Why will the query be executed twice? `fetch` does not execute query. – xdazz Aug 12 '13 at 09:25
Oh sorry I was under the assumption it did – Adam Aug 12 '13 at 09:30

score 1 · Accepted Answer · answered Aug 12 '13 at 09:27

1

too much errors in your code, it's easier to rewrite it:

$statement = $this->db_connection->prepare("SELECT * FROM tags WHERE tag LIKE ?");
$statement->execute(array($keywords));
$rows = $statement->fetchAll();
return json_encode($rows);

answered Aug 12 '13 at 09:27

Your Common Sense

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PHP PDO ALlowed Memory Exhausted when allocating 64 bytes

3 Answers3