Question

I have an array of strings of the format “Year-Month_ID”. I’d like to split each item in two at the ‘_’. Then, for the items that have the same prefix (year & month), join the IDs with ‘_’ after the prefix (“Year-Month_ID_ID…”). For example, if I have the data:

array(
    '2010-December_9',
    '2010-December_19',
    '2011-June_4',
    '2011-September_38',
    '2011-November_29',
    '2011-November_9'
)

I want the result to be:

array(
    '2010-December_9_19',
    '2011-June_4',
    '2011-September_38',
    '2011-November_29_9'
)

How can I do this?

Answer 1

$arr = array();
foreach ($dates as $val)
{   
    $tmp = explode("_", $val);
    if ( ! isset($arr[$tmp[0]]))
    {   
        $arr[$tmp[0]] = array();
    }   
    $arr[$tmp[0]][] = $tmp[1];
}   
$final = array();
foreach ($arr as $key=>$val)
{   
    $final[] = $key."_".implode("_", $val);
}