Best Way To Concatenate Strings In PHP With Spaces In Between

Question

I need to concatenate an indeterminate number of strings, and I would like a space in between two adjoining strings. Like so a b c d e f.

Also I do not want

Answer 1

$strings = array( " asd " , NULL, "", " dasd ", "Dasd  ", "", "", NULL );

function isValid($v){
return empty($v) || !$v ? false : true;
}

$concatenated = trim( implode( " ", array_map( "trim", array_filter( $strings, "isValid" ) ) ) );

//"asd dasd Dasd"