Concatenate strings in foreach loop with array key

Question

I've got a function, which takes in a string parameter for the name of specific page section, this can either be head or body.

The function looks like this:

private $html = [];

public function doStuff($pageSection, array $views)
{
    foreach ($views as $view) {
        //Do some other stuff with view

        $this->html[$pageSection] .= $view->renderOutput();
    }

    print_r($this->html);
}

The renderOutput() function from $view returns a string, and isn't throwing any errors.

When trying to add this string to the $this->html array in a specific array key (the $pageSection), I get the following error:

Notice: Undefined index: body in C:\file.php on line 35

While in the next line (print_r($this->html);, the array is filled with all the strings I wanted to add in the right array key, body.

The function get's called like this:

doStuff('body', array(
           //Array of views
         ));

I tried to remove the concatenate operator and just change the string inside the array key, this threw the same error.

How is this happening? Since I already added the array key in the $this->html[$pageSection] part.

Also, how can I fix this problem?

I Don't see anything with body here. Maybe it's in renderOutput? — u_mulder
– u_mulder, Commented May 21, 2016 at 11:33

u_mulder · Accepted Answer · 2016-05-21 11:39:43Z

2

String

$this->html[$pageSection] .= 'some data';

means that you concatenate 'some data' to value that should already exist.

In case you don't have key 'body' in $this->html and trying to concatenate to it - you'll see this notice.

You can try something like:

foreach ($views as $view) {
    //Do some other stuff with view

    // init value with empty string.
    if (!isset($this->html[$pageSection])) {
        $this->html[$pageSection] = '';  
    }

    $this->html[$pageSection] .= $view->renderOutput();
}

answered May 21, 2016 at 11:39

u_mulder

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5 Comments

Pevara Over a year ago

may I suggest to move that check outside the foreach loop. No need to check it on each iteration, since the $pageSection is constant.

Bas Over a year ago

This did the job! thank you. But why is it possible when you're not in a loop and do something like $array['randKey'] = 123; it works without the error?

u_mulder Over a year ago

Because $array['randKey'] = 123; means create key randKey and assign 123 to it. See - there's no concatenation. Check $array['randKey'] .= 123; and you will get a warning.

Bas Over a year ago

It gave the same error when I tried to just assign the string to the array key?

u_mulder Over a year ago

No, it won't. See the difference between assigning = and concatenating .=.

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