You should use recursion.
Here an exemple of code:
$datas = array(
array('id' => 1, 'parent' => 0, 'name' => 'Page 1'),
array('id' => 2, 'parent' => 1, 'name' => 'Page 1.1'),
array('id' => 3, 'parent' => 2, 'name' => 'Page 1.1.1'),
array('id' => 4, 'parent' => 3, 'name' => 'Page 1.1.1.1'),
array('id' => 5, 'parent' => 3, 'name' => 'Page 1.1.1.2'),
array('id' => 6, 'parent' => 1, 'name' => 'Page 1.2'),
array('id' => 7, 'parent' => 6, 'name' => 'Page 1.2.1'),
array('id' => 8, 'parent' => 0, 'name' => 'Page 2'),
array('id' => 9, 'parent' => 0, 'name' => 'Page 3'),
array('id' => 10, 'parent' => 9, 'name' => 'Page 3.1'),
array('id' => 11, 'parent' => 9, 'name' => 'Page 3.2'),
array('id' => 12, 'parent' => 11, 'name' => 'Page 3.2.1'),
);
function generatePageTree($datas, $parent = 0, $depth=0){
$ni=count($datas);
if($ni === 0 || $depth > 1000) return ''; // Make sure not to have an endless recursion
$tree="<ul>";
for($i=0; $i < $ni; $i++){
if($datas[$i]['parent'] == $parent){
$tree .= '<li>';
$tree .= $datas[$i]['name'];
$tree .= generatePageTree($datas, $datas[$i]['id'], $depth+1);
$tree .= '</li>';
}
}
$tree .= '</ul>';
return $tree;
}
echo(generatePageTree($datas));
You can test it at: http://phpfiddle.org/main/code/1qy-5fj
Or if you want the exact format:
function generatePageTree($datas, $parent = 0, $depth = 0){
$ni=count($datas);
if($ni === 0 || $depth > 1000) return ''; // Make sure not to have an endless recursion
$tree="";
for($i=0; $i < $ni; $i++){
if($datas[$i]['parent'] == $parent){
$tree .= str_repeat('-', $depth);
$tree .= $datas[$i]['name'] . '<br/>';
$tree .= generatePageTree($datas, $datas[$i]['id'], $depth+1);
}
}
return $tree;
}
The test: http://phpfiddle.org/main/code/jw3-s1j