二维数组去重保持索引

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$arr = array(
array('id' => 123, 'name' => 'php'),
  array('id' => 123, 'name' => 'javascript'),
  array('id' => 124, 'name' => 'python'),
  array('id' => 123, 'name' => 'php'),
  array('id' => 125, 'name' => 'node')
);

foreach ($arr as $v){
           $v = implode(",",$v);
           $a[] = $v;
       }
       $a = array_unique($a);$b= array();   
      foreach ($a as $k => $v){
          $b[$k] = explode(",",$v);
      }