PHP variable value changes

Question

This problem is simpler to explain with the code. Note that functions are located in a different file and are being included on the page.

$announcements = $dbc->query($q)->results(); //Returns array of objects
$announcements = prepareMessage($announcements); //Adds html tags to values
$latest = $announcements[0]; //Assign first index to variable
$announcements = truncate($announcements); //Truncate announcement text

function prepareMessage($message) {
    foreach($message as $values => $key) {
        $key->title = '<h2>'.$key->title.'</h2>';
        $key->name = '<p>'.$key->name.'</p>';
        $key->date = '<small>'.humanDate($key->date).'</small>';
    }

    return $message;
}

function truncate($message) {
    foreach($message as $values => $key) {
        $key->announcement = substr($key->announcement, 0, 50) . '...</p>';
    }

    return $message;
}

The value of the $latest variable changes after I run this line of code

$announcements = truncate($announcements);

$latest value before that line is ran

[announcement] =>
Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod
tempor incididunt ut labore et dolore magna aliqua.

$latest value after that line is ran

[announcement] =>
Lorem ipsum dolor sit amet, consectetur adipisc...

So my question is, why is the value of $latest changing?

Nothing in this code seems to be messing with $latest... perhaps something in the code that outputs $latest to the screen? — Solrac
– Solrac, Commented Apr 17, 2015 at 18:55

M. Adam Kendall · Accepted Answer · 2015-04-17 18:55:31Z

4

Because $latest is a reference to $announcements[0], not the actual value of $announcements[0]. Instead, use a clone. In PHP5, object assignments are always by reference.

$latest = clone $announcements[0]; //Clone first object in array

answered Apr 17, 2015 at 18:55

M. Adam Kendall

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1 Comment

DiddleDot Over a year ago

Thank you. I was not aware that it was only a reference. I will take note of that for future reference.

Rein Baarsma · Accepted Answer · 2015-04-17 18:54:57Z

2

Maybe this example will help you understand why $latest is changing:

As stated in your code $announcements is an array of objects, simplified it's like this:

$test = array(new StdClass(array('a'=>1)));
$latest = $test[0];
$test[0]->a = 3;
var_dump($latest);

The var_dump will show you $latest also changed. This is because actually $test[0] is only a reference to the instance of the StdClass, and that instance is copied to $latest. When the instance changes, both references to the instance will show you the same values, from the same instance.

answered Apr 17, 2015 at 18:54

Rein Baarsma

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Comments

Chris Mackie · Accepted Answer · 2015-04-17 18:51:38Z

0

you are cutting the value of $latest to 50 characters with the truncate function in your code.

To get the full value of $latest use the code below:

$announcements = $dbc->query($q)->results(); //Returns array of objects
$announcements = prepareMessage($announcements); //Adds html tags to values
$latest = $announcements[0]; //Assign first index to variable


function prepareMessage($message) {
    foreach($message as $values => $key) {
        $key->title = '<h2>'.$key->title.'</h2>';
        $key->name = '<p>'.$key->name.'</p>';
        $key->date = '<small>'.humanDate($key->date).'</small>';
    }

    return $message;
}

Or you can change the amount of characters to display on this line (where "50" are the amount of characters to show and "0" is where to start from)

$key->announcement = substr($key->announcement, 0, 50) . '...</p>';

edited Apr 17, 2015 at 18:51

answered Apr 17, 2015 at 18:46

Chris Mackie

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4 Comments

Solrac Over a year ago

He is applying truncate() to $announcements... now unless $latest is a reference this won't answer his question. :)

Rein Baarsma Over a year ago

I don't think your answer is really explaining why changing the value on $announcement[0] also changes the value in $latest.

Solrac Over a year ago

M. Adam Kendall's answer explains exactly why and how... op didn't mention which php version was using.

Chris Mackie Over a year ago

but its not explaining why the value is cut off (changing) as stated in the question?

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