PHP Notice: Undefined index when looping array

Question

I'm looping a two-dimensional array like this:

if (!empty($aka)) {
    foreach ($aka as $ak) {
        if($ak["lang"]=="es") {
            $sptitle=$ak["title"];
        }
    }
}

Pretty simple. If the array ($aka) is not empty I loop trough it and when it finds that the "lang" index is equal to "es" I just save the "title" value for that index in $sptitle.

The problem is that the array ($aka) contains a lot of information and sometimes there is no "lang" index... and I get this error: Notice: Undefined index: lang.

How can I fix this???

This is a extract of the array to help you understand. Notice that [1] doesn't have a [lang] index but [2] does have:

[1] => Array
    (
        [title] => "The Lord of the Rings: The Motion Picture"
        [year] => ""
        [country] => "USA"
        [comment] => "promotional title"
    )

[2] => Array
    (
        [title] => "Señor de los anillos: La comunidad del anillo, El"
        [year] => ""
        [country] => "Argentina"
        [comment] => "Chile, Mexico, Peru, Spain"
        [lang] => "es"
    )

Thanks!

Paul Dixon · Accepted Answer · 2009-03-14 12:28:39Z

16

Just test for it with isset, e.g.

if (!empty($aka)) {
        foreach ($aka as $ak) {
                if(isset($ak["lang"]) && ($ak["lang"]=="es")) {
                        $sptitle=$ak["title"];
                }
        }
}

If you're unaware of how a boolean operator like && can be short circuited, if the first operand is false, then the second operand won't be evaluated. You'll often see this idiom employed in checking for the availablilty of something before acting on it in the second operand.

You could also use array_key_exists('lang', $aka) instead of isset, it has slightly different semantics though - it will return true if an element is set to null, whereis isset would return false.

Interestingly, isset is at least twice as fast as array_key_exists, possibly due to the fact that it is a language construct rather than a regular function call.

edited Mar 14, 2009 at 12:28

answered Mar 14, 2009 at 11:25

Paul Dixon

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3 Comments

enobrev Over a year ago

I personally prefer array_key_exists, but use isset specifically because it's (surprisingly) a LOT faster us.php.net/manual/en/function.array-key-exists.php#82867

cletus Over a year ago

Um, isset($ak['lang']) will still raise an E_NOTICE of undefined index. array_key_exists() will not.

Paul Dixon Over a year ago

isset will not raise a notice, try it.

Justin Lawrence · Accepted Answer · 2010-06-17 15:09:32Z

0

would it be wrong to use:

if (@$ak['lang'])

i really miss the fact that we can't still do the 2 checks in 1 like so

if ($ak['lang'])

it was one of the beautiful things about PHP and I just don't see the purpose of warning whether an array key is initialised in a transient scripting language like PHP.

i'm not sure where the developers of PHP are going with this. personally, i'm a bit worried that they're morphing PHP into something else. just leave it alone. it was great.

answered Jun 17, 2010 at 15:09

Justin Lawrence

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1 Comment

Unsigned Over a year ago

The manual states on this page: "In PHP 4 and PHP 5 the default value is E_ALL & ~E_NOTICE. This setting does not show E_NOTICE level errors." The display of this E_NOTICE is a configuration issue, not a PHP problem.

John Conde · Accepted Answer · 2012-11-05 17:01:29Z

0

if (@!empty($aka)) {
        foreach ($aka as $ak) {
                if($ak["lang"]=="es") {
                        $sptitle=$ak["title"];
                }
        }
}

or


if ( @$_POST['value'] == 'yes' ) 
 {
   state;
 }

in most cases this noticed removed by using @ sign.............

edited Nov 5, 2012 at 17:01

John Conde

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answered Nov 29, 2011 at 12:30

alpesh purohit

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