PHP：将一个数组的值设置为另一个数组

I want to create a new array, and set its keys equal to the values of another array.

Start:

$names = array("don","james","jennifer","paul");
$ages = array("don" => 25, "paul" => 32);

Finish:

$name_age_map = array(
 "don" => 25,
 "james" => null,
 "jennifer" => null,
 "paul" => 32,
);

How should this be done in PHP? This is the best I've got so far:

$name_age_map = array();
foreach ($names as $name) {
  $name_age_map[$name] = $name_map[$name]; 
}

Ideally I wouldn't even create a new array, I'd just give element in $names a value of the age.

array_merge(
   array_combine(
       $names,
       array_fill(0,count($names),NULL)
   ),
   $ages);

$name_map = array();
foreach ($names as $name) {
  $name_map[$name] = isset($ages[$name])?$ages[$name]:null; 
}

The problem is the values in $names are just that - values. To make them 'equal' an age, you need them to be keys. Because PHP doesn't support passing keys by reference, that means creating a new array:

$name_age_map = array();
foreach($names as $name) {
    if(isset($ages[$name])) {
        $name_age_map[$name] = $ages[$name];
    }
    else {
        $name_age_map[] = $name;
    }
}

Or if you always want names to be keys (which probably makes more sense):

$name_age_map = array();
foreach($names as $name) {
    $name_age_map[$name] =
            isset($ages[$name]) ? $ages[$name] : null;
}

$name_age_map = array();

foreach ($names as $name){
    // this can also be replaced with
    // if (array_key_exists($name, $ages)){
    if (in_array($name, array_keys($ages))){
        $name_age_map[$name] = $ages[$name];
    }
    else {
        $name_age_map[$name] = null;
    }
}

To manipulate the original array you need to flip it and then add the associated ages.

Try this:

$names = array_flip($names);
foreach($names as $key => $value)
{
    $names[$key] = (array_key_exists($key,$ages)) ? $ages[$key] : null;
}

array_key_exists() can help you when comparing keys in two array. Apply a loop and assign values where matches are found or null otherwise. This should work out for you.

$names = array("don","james","jennifer","paul");
$ages = array("don" => 25, "paul" => 32);

$merged = array();
foreach($names as $n) {
    if(array_key_exists($n, $ages)) {
        $merged[$n] = $ages[$n];
    } else {
        $merged[$n] = null;
    }
}

var_dump($merged);

//Produces

array(4) {
  ["don"]=>
  int(25)
  ["james"]=>
  NULL
  ["jennifer"]=>
  NULL
  ["paul"]=>
  int(32)
}

Just for fun, you could do it like this:

$names = array("don","james","jennifer","paul");
$ages  = array("don" => 25, "paul" => 32);
$names = array_merge(array_fill_keys($names, null), $ages);

var_dump($names);

Yields:

array(4) {
  ["don"]=>
  int(25)
  ["james"]=>
  NULL
  ["jennifer"]=>
  NULL
  ["paul"]=>
  int(32)
}