<?php

foreach ($_REQUEST as $key => $value) {
    if (trim($value)) {
        $values = preg_split("/[\s,]+/", $value);
        foreach ($values as $v) {
            echo $v . '\n';
        }
    }
}

这个和算法有关系吗？

<?php
$_REQUEST = ['a' => 'a,b,c', 'b' => '', 'c' => 'a,d　c0 ,0'];
$arr = [];
foreach($_REQUEST as $v) {
    $v = str_replace("　", ',', $v);
    $v = trim($v, ' ,');
    $v = explode(',', $v);
    foreach($v as $_v) {
        $_v = trim($_v);
        if (strlen($_v)) $arr[] = $_v;
    }
}
print_r($arr);
echo count($arr);
/*
Array
(
    [0] => a
    [1] => b
    [2] => c
    [3] => a
    [4] => d
    [5] => c
    [6] => c0
    [7] => 0
)
8
*/