Simple usage sharing of PHP singleton mode

This article mainly introduces the simple usage of PHP singleton mode, and analyzes the specific implementation methods and usage skills of PHP singleton mode in the form of database operation class examples. Friends who need it can refer to it. I hope it can help everyone.

<?php
class db {
  public $conn;
  public static $sql;
  public static $instance=null;
  private function __construct(){
    require_once(&#39;db.config.php&#39;);
    $this->conn = mysql_connect($db[&#39;host&#39;],$db[&#39;user&#39;],$db[&#39;password&#39;]);
    if(!mysql_select_db($db[&#39;database&#39;],$this->conn)){
      echo "失败";
    };
    mysql_query(&#39;set names utf8&#39;,$this->conn);
  }
  public static function getInstance(){
  if(is_null(self::$instance)){
    self::$instance = new self();
  }
    return self::$instance;
  }
  /**
  * 查询数据库
  */
  public function select($table,$condition=array(),$field = array()){
    $where=&#39;&#39;;
    if(!empty($condition)){
      foreach($condition as $k=>$v){
        $where.=$k."=&#39;".$v."&#39; and ";
      }
      $where=&#39;where &#39;.$where .&#39;1=1&#39;;
    }
    $fieldstr = &#39;&#39;;
    if(!empty($field)){
      foreach($field as $k=>$v){
        $fieldstr.= $v.&#39;,&#39;;
      }
      $fieldstr = rtrim($fieldstr,&#39;,&#39;);
    } else {
      $fieldstr = &#39;*&#39;;
    }
    self::$sql = "select {$fieldstr} from {$table} {$where}";
    $result=mysql_query(self::$sql,$this->conn);
    $resuleRow = array();
    $i = 0;
    while($row=mysql_fetch_assoc($result)){
      foreach($row as $k=>$v){
        $resuleRow[$i][$k] = $v;
      }
    $i++;
    }
    return $resuleRow;
  }
  //添加一条记录
  public function insert($table,$data) {
    $values = &#39;&#39;;
    $data = &#39;&#39;;
    foreach ($data as $k=>$v) {
      $values .= $k.&#39;,&#39;;
      $datas .= "&#39;$v&#39;".&#39;,&#39;;
    }
    $values = rtrim($values,&#39;,&#39;);
    $datas = rtrim($datas,&#39;,&#39;);
    self::$sql = "INSERT INTO {$table} ({$values}) VALUES ({$datas})";
    if(mysql_query(self::$sql)) {
      return mysql_insert_id();
    } else {
      return false;
    }
  }
  //修改一条记录
  public function update($table,$data,$condition=array()){
    $where=&#39;&#39;;
    if(!empty($condition)) {
    foreach($condition as $k=>$v) {
      $where.=$k."=&#39;".$v."&#39; and ";
    }
      $where=&#39;where &#39;.$where .&#39;1=1&#39;;
    }
    $updatastr = &#39;&#39;;
    if(!empty($data)) {
    foreach($data as $k=>$v) {
      $updatastr.= $k."=&#39;".$v."&#39;,";
    }
      $updatastr = &#39;set &#39;.rtrim($updatastr,&#39;,&#39;);
    }
    self::$sql = "update {$table} {$updatastr} {$where}";
    return mysql_query(self::$sql);
  }
  //删除记录
  public function delete($table,$condition) {
    $where=&#39;&#39;;
    if(!empty($condition)) {
      foreach($condition as $k=>$v) {
        $where.=$k."=&#39;".$v."&#39; and ";
      }
      $where=&#39;where &#39;.$where .&#39;1=1&#39;;
    }
    self::$sql = "delete from {$table} {$where}";
    return mysql_query(self::$sql);
  }
  public static function getLastSql() {
    echo self::$sql;
  }
}
$db = db::getInstance();
//$list = $db->select(&#39;demo&#39;,array(&#39;name&#39;=>&#39;tom&#39;,&#39;password&#39;=>&#39;ds&#39;),array(&#39;name&#39;,&#39;password&#39;));
//echo $db->insert(&#39;demo&#39;,array(&#39;name&#39;=>&#39;最近你啦&#39;,&#39;password&#39;=>&#39;123&#39;));
//echo $db->update(&#39;demo&#39;,array("name"=>&#39;xxx&#39;,"password"=>&#39;123&#39;),array(&#39;id&#39;=>1));
echo $db->delete(&#39;demo&#39;,array(&#39;id&#39;=>&#39;2&#39;));
db::getLastSql();
echo "<pre class="brush:php;toolbar:false">";
?>

Related recommendations:

MongoDB singleton mode instance operation sharing implemented in php

How to implement singleton mode in php

The difference between factory mode and singleton mode in php design mode

The above is the detailed content of Simple usage sharing of PHP singleton mode. For more information, please follow other related articles on the PHP Chinese website!