Warning: Invalid argument supplied for foreach()

配列じゃないのをforeachに渡しちゃうとwarningウザい ⇒ 全部配列にすればいい

<?php
function toa($s)
{
    is_array($s) or $s=array($s);
    return $s;
}

$list = 0;
foreach( $list as $a ){
    print("$a\n");    // Invalid argument supplied for foreach()
}

$list = array(1,2,3);
foreach( toa($list) as $a ){
    print("$a\n");    // 1 2 3
}

$list = 4;
foreach( toa($list) as $a ){
    print("$a\n");    // 4
}
?>