Queue of data structure--sequential storage structure (PHP code Implementation-method I)

<?php/** *  the first--non-cyclic sequential queue implementation Method  *  the head element of the queue is the element labeled 0 in the array  *  the advantages and disadvantages of this method: *    Advantage: The head element is always labeled as the first element of  0 , so there is no need to set the head pointer  *   disadvantage: The element will move a lot of elements, the time complexity is O (n), the efficiency is relatively low  *  */class SqQueue{    private  $SQARR;//queue storage Array     private   $rear;//If the queue is not empty, point to the last position of the tail element     public function __construct () {          $this->sqarr=array ();         $ this->rear=0;    }    //Destruction Chain Stacks     public  Function destroyqueue () {         $this->sqarr=null;          $this->rear=0;    }    //Empty queue     public function clearqueue () {          $this->sqarr=array ();         $this->rear=0;    }     //whether the queue is empty     public function queueempty () {         if ($this->rear==0) {             return  ' Null ';        }else{             return  ' No null ';         }    }    //Length of queue     public  Function queuelength () {        return  $this->rear;     }    //get team head element     public function gethead () {        return  $this->sqarr[0];    }     //inserts elements from the end of the team &Nbsp;   public function enqueue ($elem) {          $this->sqarr[$this->rear++]= $elem;     }    //remove elements from Team head      public function dequeue () {        if ($ this->rear == 0) {            return   ' ERROR ';        }         for ($i =1; $i < $this->rear; $i +) {              $this->sqarr[$i -1]= $this->sqarr[$i];        }         unset ($this->sqarr[$this->rear-1]);//After the move is complete, the last element will not exist. So let it out.          $this->rear--;         return  ' OK ';    }    //traversing queue elements     public function  Queuetraverse () {         $arr =array ();         for ($i =0; $i < $this->rear; $i +) {              $arr []= $this->sqarr[$i];        }         return  $arr;         return   $this->sqarr;    }}

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Queue of data structure--sequential storage structure (PHP code Implementation-method I)