PHP 1：1到1：很多数组

Question

I have three arrays called associativeArray keyArray and valueArray. associativeArray is an array that's made up of key/value pairs, the pairs are split up and placed into keyArray and valueArray. What I want to do now is create a fourth array called newArray that uses the elements in valueArray as its keys and have the values be from their respective keyArray. But unlike the associativeArray that has 1:1 key-to-value, I want to have newArray have 1:many key-to-value while not having any repeating keys. This is the code I made for it:

foreach($keyArray as $keyElement){
    $valueElement = $associativeArray[$keyElement];
    if (!in_array($valueElement,$newArray)){
        array_push($newArray, $valueElement => array($keyElement));
    }
    else{
        array_push($newArray[$valueElement],$keyElement);
    }
}

However whenever I run it I get:

PHP Parse error:  syntax error, unexpected T_DOUBLE_ARROW

Answer 1

You don't need all those arrays. Just associativeArray is enough.

You can do it like this:

$newArray = array();
// This will loop in the array so that, in each step:
//  - $k is the current key
//  - $v is the current value
foreach($associativeArray as $k => $v) {
    // If newArray doesn't already have $v as a key
    if (!array_key_exists($v, $newArray)) {
        // Define it as a new array with only one element
        $newArray[$v] = array($k);        
    } else {
        // If it already exists, just push $k to it's elements
        $newArray[$v][] = $k; // This is the same as array_push($newArray[$v], $k)
    }
}