php how to add key value pair to array code example

Example 1: php array push with key

<?php
$a=array("a"=>"red","b"=>"green");
array_push($a,"blue","yellow");
print_r($a);
?>

Example 2: php array push with key

// Error : "array_push() expects parameter 1 to be array, null given"
// Don't array_push($array,$arrayValueToPush); 
// Set the array value.
$array["arrayKey"] = $arrayValue;
//----------------------------------------
$newArray = [];
foreach ($arrayItems as $key => $arrayItem) {
  $newArray[$key]["arrayItemKey1"] = $arrayItem["arrayItemKey1FromArrayItem"];
  $newArray[$key]["arrayItemKey2"] = $arrayItem["arrayItemKey2FromArrayItem"];
}