了解foreach循环中的变量赋值[关闭]

Question

I have a pretty basic question:

What is this statement actually doing (specifically the =>$p)?

foreach ($email->parts as $partno=>$p) {

I understand the the basics but the =>$p is not clear

Answer 1

In a foreach loop you can ask for both the key and value to be returned

$array = array('cat' => 'Tom', 'mouse' => 'Jerry');
foreach($array as $animal => $name) {
    echo $name . ' is a ' . $animal . '<br>';
}

So the loop will output

Tom is a cat
Jerry is a mouse

Answer 2

This synthax is to assign the array key name or object property name to the variable $partno and it's value to $p.

This way you can do for instance $email->parts[$partno] = $p;.

It can be particularly useful if you have parallel arrays with different information bound by the key, so you need this information to obtain related data from the other array when iterating one of them.

For instance:

$person = array(
    1 => 'Santa Claus',
    2 => 'Homer Simpson',
    3 => 'Papa Smurf'
);

$location = array(
    1 => 'North Pole',
    2 => 'Springfield',
    3 => 'Smurf village'
);

foreach ($person as $id => $name)
    echo "$name live in {$location[$id]}
";

Answer 3

$partno is the key, $p is value e.g. $email->parts = array("key" => "value");

Read this

http://www.php.net/manual/en/control-structures.foreach.php