Online PHP editor | output for hL7RH

<?php $subjects = array( array( 'class' => 'one', 'sub' => 'music', ), array( 'class' => 'one', 'sub' => array( 'social', 'health', 'science' ), ), array( 'class' => 'two', 'sub' => 'music', ), array( 'class' => 'one', 'sub' => 'math', ) ); $class_sub = array(); $result = array(); foreach( $subjects as $sub ) { if ( ! isset( $class_sub[ $sub['class'] ] ) ) { $class_sub[ $sub['class'] ] = $sub['sub']; } else { if ( is_array( $class_sub[ $sub['class'] ] ) ) { $new = array_merge( $class_sub[ $sub['class'] ], is_array($sub['sub']) ? $sub['sub'] : array($sub['sub'])); } else { $new = array_merge( array($class_sub[ $sub['class'] ]), is_array($sub['sub']) ? $sub['sub'] : array($sub['sub'])); } $class_sub[ $sub['class'] ] = $new; } } foreach( $class_sub as $class => $sub ) { $result[] = array( 'class' => $class, 'sub' => $sub ); } echo "<pre>"; print_r( $result ); echo "</pre>";