Comprehensive analysis of the source code of thinkphp3.2.0 setInc method

<?php
namespace Home\Controller;
use Think\Controller;

class TestController extends Controller {
  public function test() {
    $tb_test = M(&#39;test&#39;);
    $tb_test->where([&#39;id&#39;=>1])->setInc(&#39;test_number&#39;,2); //每次添加2
    dump($tb_test->getLastSql());
    //string(67) "UPDATE `tb_test` SET `test_number`=test_number+2 WHERE ( `id` = 1 )"
  }
}

/**
   * 字段值增长
   * @access public
   * @param string $field 字段名
   * @param integer $step 增长值
   * @return boolean
   */
  public function setInc($field,$step=1) {
    return $this->setField($field,array('exp',$field.'+'.$step));
  }

/**
   * 设置记录的某个字段值
   * 支持使用数据库字段和方法
   * @access public
   * @param string|array $field 字段名
   * @param string $value 字段值
   * @return boolean
   */
  public function setField($field,$value='') {
    if(is_array($field)) {
      $data      =  $field;
    }else{
      $data[$field]  =  $value;
    }
    return $this->save($data);
  }

/**
   * 保存数据
   * @access public
   * @param mixed $data 数据
   * @param array $options 表达式
   * @return boolean
   */
  public function save($data='',$options=array()) {
    if(empty($data)) {
      // 没有传递数据，获取当前数据对象的值
      if(!empty($this->data)) {
        $data      =  $this->data;
        // 重置数据
        $this->data   =  array();
      }else{
        $this->error  =  L('_DATA_TYPE_INVALID_');
        return false;
      }
    }
    // 数据处理
    $data    =  $this->_facade($data);
    // 分析表达式
    $options  =  $this->_parseOptions($options);
    $pk     =  $this->getPk();
    if(!isset($options['where']) ) {
      // 如果存在主键数据 则自动作为更新条件
      if(isset($data[$pk])) {
        $where[$pk]     =  $data[$pk];
        $options['where']  =  $where;
        unset($data[$pk]);
      }else{
        // 如果没有任何更新条件则不执行
        $this->error    =  L('_OPERATION_WRONG_');
        return false;
      }
    }
    if(is_array($options['where']) && isset($options['where'][$pk])){
      $pkValue  =  $options['where'][$pk];
    }    
    if(false === $this->_before_update($data,$options)) {
      return false;
    }    
    $result   =  $this->db->update($data,$options);
    if(false !== $result) {
      if(isset($pkValue)) $data[$pk]  = $pkValue;
      $this->_after_update($data,$options);
    }
    return $result;
  }

/**
   * 更新记录
   * @access public
   * @param mixed $data 数据
   * @param array $options 表达式
   * @return false | integer
   */
  public function update($data,$options) {
    $this->model =  $options['model'];
    $sql  = 'UPDATE '
      .$this->parseTable($options['table'])
      .$this->parseSet($data)
      .$this->parseWhere(!empty($options['where'])?$options['where']:'')
      .$this->parseOrder(!empty($options['order'])?$options['order']:'')
      .$this->parseLimit(!empty($options['limit'])?$options['limit']:'')
      .$this->parseLock(isset($options['lock'])?$options['lock']:false)
      .$this->parseComment(!empty($options['comment'])?$options['comment']:'');
    return $this->execute($sql,$this->parseBind(!empty($options['bind'])?$options['bind']:array()));
  }

/**
   * 执行语句
   * @access public
   * @param string $str sql指令
   * @return integer|false
   */
  public function execute($str) {
    $this->initConnect(true);
    if ( !$this->_linkID ) return false;
    $this->queryStr = $str;
    //释放前次的查询结果
    if ( $this->queryID ) {  $this->free();  }
    N('db_write',1);
    // 记录开始执行时间
    G('queryStartTime');
    $result =  mysql_query($str, $this->_linkID) ;
    $this->debug();
    if ( false === $result) {
      $this->error();
      return false;
    } else {
      $this->numRows = mysql_affected_rows($this->_linkID);
      $this->lastInsID = mysql_insert_id($this->_linkID);
      return $this->numRows;
    }
  }