真诚自定义，多谢

function foo($s) {
  $dict = array_flip(explode(',', '/,monday,tuesday,wednesday,thursday,friday,saturday,sunday'));
  $dict['/'] = ',';
  return strtr(strtolower($s), $dict);
}

echo foo('Monday/Tuesday/Wednesday/Thursday/Friday/Saturday/Sunday');

function foo($s) {
	$array=array('monday'=>1,
							'tuesday'=>2,
							'wednesday'=>3,
							'thursday'=>4,
							'friday'=>5,
							'saturday'=>6,
							'sunday'=>7,
							'/'=>',',' '=>',');
  return strtr(strtolower($s), $array);
} 
echo foo('Monday Tuesday Wednesday/Thursday/Friday/Saturday/Sunday');

function foo($s) {
    $array= array('monday'   => 1,
                 'tuesday'  => 2,
                 'wednesday'=> 3,
                 'thursday' => 4,
                 'friday'   => 5,
                 'saturday' => 6,
                 'sunday'   => 7,
                );

    $sa = preg_split('/\W/',strtolower($s));
    $arr = array();
    foreach ($sa as $v) {
        if(is_numeric($v)) {
            $t = array_values($array);
            $arr[] = $t[$v-1];
        }
        else if (isset($array[$v])) {
            $arr[] = $array[$v];
        }
        else {
            foreach ($array as $k1 => $v1 )  {
                if ( substr($k1, 0, 4) == $v ) {
                    $arr[] = $v1; break;
                }