[PHP]配列内から、index指定で要素を削除する方法

// 先頭を削除
echo "case1----\n";
$dataList = array( "d1", "d2", "d3", "d4", "d5" );
array_shift( $dataList );
var_dump( $dataList );
 
// 末尾を削除
echo "case2----\n";
$dataList = array( "d1", "d2", "d3", "d4", "d5" );
array_pop( $dataList );
var_dump( $dataList );
 
// 2個目の要素を削除
echo "case3----\n";
$dataList = array( "d1", "d2", "d3", "d4", "d5" );
unset( $dataList[1] );
var_dump( $dataList );

case1----
array(4) {
  [0]=>
  string(2) "d2"
  [1]=>
  string(2) "d3"
  [2]=>
  string(2) "d4"
  [3]=>
  string(2) "d5"
}
 
case2----
array(4) {
  [0]=>
  string(2) "d1"
  [1]=>
  string(2) "d2"
  [2]=>
  string(2) "d3"
  [3]=>
  string(2) "d4"
}
 
case3----
array(4) {
  [0]=>
  string(2) "d1"
  [2]=>
  string(2) "d3"
  [3]=>
  string(2) "d4"
  [4]=>
  string(2) "d5"
}

// $dataList[2]を削除して、配列indexをスライドさせる
echo "case4----\n";
$dataList = array( "d1", "d2", "d3", "d4", "d5" );
$delIndex = 2;
$dataList = array_merge( array_slice( $dataList, 0,           $delIndex                    ),
                         array_slice( $dataList, $delIndex+1, count($dataList) - $delIndex ) );
var_dump( $dataList );

case4----
array(4) {
  [0]=>
  string(2) "d1"
  [1]=>
  string(2) "d2"
  [2]=>
  string(2) "d4"
  [3]=>
  string(2) "d5"
}

unset( $dataList[ 'keyValue1' );