Question

$posts = array(
"message" => 'this is a test message'
);

foreach ($posts as $post) {
     echo $post['message'];
}

为什么上面的代码只输出消息中的第一个字母？ “T”。

谢谢！

Answer 1

foreach获取数组的每个元素并将其赋值给变量。为了得到结果，我假设您只是需要这样做：

foreach ($posts as $post) {
   echo $post;
}

有关代码无法工作的具体细节：$post将是数组元素的内容 - 在本例中为字符串。因为PHP不是强类型/支持类型杂耍，所以你实际上可以使用字符串，就像它是一个数组一样，并获取序列中的每个字符：

foreach ($posts as $post) {
    echo $post[0]; //'t'
    echo $post[1]; //'h'
}

因此$post['message']显然不是有效的元素，并且没有从(string)'message'到int的明确转换，因此这将转变为$post[0]。

Answer 2

# $posts is an array with one index ('message')
$posts = array(
    "message" => 'this is a test message'
);

# You iterate over the $posts array, so $post contains
# the string 'this is a test message'
foreach ($posts as $post) {
    # You try to access an index in the string.
    # Background info #1:
    #   You can access each character in a string using brackets, just
    #   like with arrays, so $post[0] === 't', $post[1] === 'e', etc.
    # Background info #2:
    #   You need a numeric index when accessing the characters of a string.
    # Background info #3:
    #   If PHP expects an integer, but finds a string, it tries to convert
    #   it. Unfortunately, string conversion in PHP is very strange.
    #   A string that does not start with a number is converted to 0, i.e.
    #   ((int) '23 monkeys') === 23, ((int) 'asd') === 0,
    #   ((int) 'strike force 1') === 0
    # This means, you are accessing the character at position ((int) 'message'),
    # which is the first character in the string
    echo $post['message'];
}

你可能想要的是：

$posts = array(
    array(
        "message" => 'this is a test message'
    )
);
foreach ($posts as $post) {
    echo $post['message'];
}

或者这个：

$posts = array(
    "message" => 'this is a test message'
);
foreach ($posts as $key => $post) {
    # $key === 'message'
    echo $post;
}

Answer 3

我想补充iAn的答案：如果你想以某种方式访问值的键，请使用：

foreach ($posts as $key => $post) {
    echo $key . '=' . $post;
}

结果：

message=this is a test message

数组和foreach

3 个答案: