PHP Array sorting problem

$arr = array(        'id' => 1, 'pid' => 0, 'title' => '1',        'id' => 2, 'pid' => 0, 'title' => '2',        'id' => 3, 'pid' => 0, 'title' => '3',        'id' => 4, 'pid' => 0, 'title' => '4',        'id' => 5, 'pid' => 1, 'title' => '1-5',        'id' => 6, 'pid' => 5, 'title' => '1-5-6',        'id' => 7, 'pid' => 1, 'title' => '1-7',        'id' => 8, 'pid' => 2, 'title' => '2-8',    );

Finish sorting effect

$arr = array(        'id' => 1, 'pid' => 0, 'title' => '1',        'id' => 5, 'pid' => 1, 'title' => '1-5',        'id' => 6, 'pid' => 5, 'title' => '1-5-6',        'id' => 7, 'pid' => 1, 'title' => '1-7',        'id' => 2, 'pid' => 0, 'title' => '2',        'id' => 8, 'pid' => 2, 'title' => '2-8',        'id' => 3, 'pid' => 0, 'title' => '3',        'id' => 4, 'pid' => 0, 'title' => '4',    );

is the parent node immediately following the child node

Reply content:

$arr = array(        'id' => 1, 'pid' => 0, 'title' => '1',        'id' => 2, 'pid' => 0, 'title' => '2',        'id' => 3, 'pid' => 0, 'title' => '3',        'id' => 4, 'pid' => 0, 'title' => '4',        'id' => 5, 'pid' => 1, 'title' => '1-5',        'id' => 6, 'pid' => 5, 'title' => '1-5-6',        'id' => 7, 'pid' => 1, 'title' => '1-7',        'id' => 8, 'pid' => 2, 'title' => '2-8',    );

Finish sorting effect

$arr = array(        'id' => 1, 'pid' => 0, 'title' => '1',        'id' => 5, 'pid' => 1, 'title' => '1-5',        'id' => 6, 'pid' => 5, 'title' => '1-5-6',        'id' => 7, 'pid' => 1, 'title' => '1-7',        'id' => 2, 'pid' => 0, 'title' => '2',        'id' => 8, 'pid' => 2, 'title' => '2-8',        'id' => 3, 'pid' => 0, 'title' => '3',        'id' => 4, 'pid' => 0, 'title' => '4',    );

is the parent node immediately following the child node

 !--? Php$arr = array (' ID ' =--> 1, ' pid ' = + 0, ' title ' = = ' 1 '), array (' id ' = = 2, ' pid ' = + 0, ' title ' = ' 2 '), array (' id ' = = 3, ' pid ' = 0, ' title ' =&G T ' 3 '), array (' id ' = = 4, ' pid ' = + 0, ' title ' = ' 4 '), array (' id ' = = 5, ' pid ' = 1, ' title ' => ; ' 1-5 '), array (' id ' = = 6, ' pid ' = + 5, ' title ' = ' 1-5-6 '), array (' id ' = 7, ' pid ' = = 1, ' title ' = = ' 1-7 '), array (' id ' = = 8, ' pid ' = 2, ' title ' = ' 2-8 '), function userSort ($a, $b) {$a = $    a[' title '];    $b = $b [' title '];    if ($a = = $b) return 0; Return $a > $b? 1:-1;} Usort ($arr, ' userSort '); echo " 
 ";p rint_r ($arr);  
 
 