PHP Get Multi Select List Values

Question

I'm trying to write a simple function to construct field names for a form. It works fine if at least one value is selected in a multi-select list but if nothing is selected I get an Undefined index error. Here is what I have:

function mcFieldName($mcFieldName){
$mcField = $_POST[$mcFieldName];
if( !is_array($mcField) ){
    if( !empty($mcField) ){
        return $mcField;
    }else{
        return 'n/a';
    }
}
if( is_array($mcField) ){
    $mcFieldArray = implode(',', $mcField);
    return $mcFieldArray;
}

}

$MultiSelect = mcFieldName('mcMultiSelect');
// test
echo $MultiSelect . '<br/>';

Thank you!

Jon · Accepted Answer · 2012-01-09 02:21:32Z

1

You just need to protect yourself from reading a key that does not exist in $_POST:

$mcField = isset($_POST[$mcFieldName]) ? $_POST[$mcFieldName] : null;

answered Jan 9, 2012 at 2:21

Jon

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2 Comments

user1002039 Over a year ago

I tried the isset and !empty but neither of them worked. I don't understand the null part.

Jon Over a year ago

@user1002039: What this does is set $mcField to the field's value if one was posted, or to null if one was not. Your existing code would then react to the null value by returning "n/a". I 'm not sure what you mean "you tried and neither worked".

zerkms · Accepted Answer · 2012-01-09 02:21:32Z

1

Before you try to access an array item make sure it exists with using isset():

if (isset($_POST[$mcFieldName])) {
    $mcField = $_POST[$mcFieldName];
    ...
}

answered Jan 9, 2012 at 2:21

zerkms

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