PHP foreach 循环数据类型复杂性和值检索

Question

我试图从 foreach 循环中提取数据，但我遇到了一个我还没有遇到过的奇怪现象。

CSV 的第一行如下所示：

Part Number,Description,List Price

然后是数据等等。

我有什么：

ini_set('auto_detect_line_endings', TRUE);
if (($openItems = fopen($uploadFile, 'r')) !== FALSE) {
   foreach (fgetcsv($openItems) as $key => $value) {
        $value = preg_replace('/\h+/', '', strtolower($value));
        echo $value;
        echo ' = ' . $key . " ";
        switch ($value) {
            case "partnumber":
                $pn = $key;
                break;
            case "description":
                $des = $key;
                break;
            case "listprice":
                $lp = $key;
                break;
        }
    }
    print_r("\npn: " . $pn . " des: " . $des . " lp: " . $lp);
}

打印：

partnumber = 0 description = 1 listprice = 2 
pn:  des: 1 lp: 2

如您所见，第一列是错误的，因此未为其分配正确的值。

替代打印：

test = 0 partnumber = 1 description = 2 listprice = 3 
pn: 1 des: 2 lp: 3

在 $key 被回显后，我还尝试了一个练习：

if($value == 0) {
    echo " I'm 0 ";
}

打印：

partnumber = 0  I'm 0. description = 1  I'm 0. listprice = 2  I'm 0. 
pn:  des: 1 lp: 2

但如果你检查算术，它会返回错误：

if(is_numeric($value)) {
    echo " I'm a number. ";
}

打印不变：

partnumber = 0 description = 1 listprice = 2 
pn:  des: 1 lp: 2

这意味着它在 NULL 或错误意义上是 0 对吧？

if(!$value) {
    echo " I'm False or Null. ";
}

但打印没有改变：

partnumber = 0 description = 1 listprice = 2 
pn:  des: 1 lp: 2

类型检查：

echo "I'm of Type ". gettype($value) . ". ";

返回：

partnumber = 0 I'm of Type string. description = 1 I'm of Type string. listprice = 2 I'm of Type string. 

旁注：

case "partnumber":
    $pn = $key;
    break;

从未访问过

case "partnumber":
    $pn = $key;
    echo "I Worked!";
    break;

返回没有任何结果。

有什么建议吗？

感谢@azjezz

$csv = [];
ini_set('auto_detect_line_endings', TRUE);
if (($openItems = fopen($uploadFile, 'r')) !== FALSE) {
    foreach (fgetcsv($openItems) as $key => $value) {
        $value = preg_replace('/\h+/', '', strtolower($value));
        $csv[$value] = (Int) $key;
        echo $value;
        echo ' = ' . $key . " ";
        switch ($csv[$value]) {
            case "partnumber":
                $pn = $key;
                break;
            case "description":
                $des = $key;
                break;
            case "listprice":
                $lp = $key;
                break;
        }
    }
    print_r("\npn: " . $pn . " des: " . $des . " lp: " . $lp);
}

结果：

partnumber = 0 description = 1 listprice = 2 
pn: 0 des:  lp: 

另一个奇怪的场景：

    switch ((int) $value) {
        case "partnumber":
            $pn = $key;
            break;
        case "description":
            $des = $key;
            break;
        case "listprice":
            $lp = $key;
            break;
    }

返回：

partnumber = 0 description = 1 listprice = 2 
pn: 2 des:  lp: 

Answer 1

将所有值转换为integer，然后使用$csv 数组。

$csv = [];
foreach (fgetcsv($openItems) as $key => $value) {
  $csv[$value] = (Int) $key;
}

var_dump($csv);

注意 == 和 === 是不一样的！

<?php 

$a = 0;
$b = "0";

// == is the Equal Comparison Operator
//if $a is equal to $b after type juggling.
if($a == $b) {
  echo "YES ITS TRUE";
}

// === is the Identical Comparison Operator
//  if $a is equal to $b, and they are of the same type. 
if($a === $b) {
  echo "Is it ?";
} else {
  echo "well its not";
}

您可以在此处阅读有关比较运算符的更多信息：http://php.net/manual/en/language.operators.comparison.php