Detailed explanation of the wp_parse_args function used to synthesize arrays in WordPress

The

wp_parse_args() function is a frequently used function in the core of WordPress. It has many uses, but it is mainly used to bind a default value to an array parameter (args).

Because the wp_parse_args() function must return an array, it will automatically convert the incoming query string and object into an array, giving users more convenient conditions and increasing compatibility.

The common query_posts(), wp_list_comments() and get_terms() functions all use the wp_parse_args() function to help them add default values ​​to array parameters.

Usage

wp_parse_args( $args, $defaults );

Parameters

$args

(array | string) (required) Query string, object or array parameters, used to bind default values.

Default: None

Query string:

type=post&posts_per_page=5&cat=1

Array:

array( 'type' => 'post', 'posts_per_page' => 5, 'cat' => '1' )

$defaults

(Array) (Optional) Default parameters for the array parameter.

Default value: empty string

Example

function explain_parse_args( $args = array() ){
 
  //$args 的默认值
  $defaults = array(
    'before' => '<div>',
    'after' => '</div>',
    'echo' => true,
    'text' => 'wp_parse_args() 函数演示'
  );
 
  //绑定默认值
  $r = wp_parse_args( $args, $defaults );
 
  $output = $r['before'] . $r['text'] . $r['after'];
  if( !$r['echo'] ) return $output;
  echo $output;
}
 
//没有参数
explain_parse_args();//打印：<div>wp_parse_args() 函数演示</div>
 
//字符串参数
$output = explain_parse_args( 'text=字符串参数&before=<div>&echo=0' );
echo $output;//打印：<div>字符串参数</div>
 
//数组参数
explain_parse_args( array( 'text' => '数组参数', 'before' => '<div>' ) );//打印：<div>数组参数</div>
还有另一种不使用第二个 $defaults 参数的用法，就是帮你把一个查询字符串、对象或者数组的变量直接转换成通用的数组，避免判断类型。

//字符串
$array = wp_parse_args( 'text=测试另一种用法&type=字符串' );
var_dump( $array );
/*
  array(2) {
    ["text"]=>
      string(21) "测试另一种用法"
    ["type"]=>
      string(9) "字符串"
  }
*/
 
//对象（object）
class args_obj{
 
  public $text = '测试另一种用法';
 
  public $type = '对象（object）';
 
  function func(){
    //转换成数组的时候对象里边的函数会被忽略
  }
 
}
$obj = new args_obj;
var_dump( $obj );
/*
object(args_obj)#2175 (2) {
  ["text"]=>
    string(21) "测试另一种用法"
  ["type"]=>
    string(18) "对象（object）"
}
*/

wp_parse_args function source code details The source code of this function:

/**
 * Merge user defined arguments into defaults array.
 *
 * This function is used throughout WordPress to allow for both string or array
 * to be merged into another array.
 *
 * @since 2.2.0
 *
 *第一个参数可以是 字符串、数组或对象（obj）
 * @param string|array $args Value to merge with $defaults
 *第二个参数为默认的预设值数组，必须是数组
 * @param array $defaults Array that serves as the defaults.
 *返回值将是一个数组
 * @return array Merged user defined values with defaults.
 */
function wp_parse_args( $args, $defaults = '' ) {
 if ( is_object( $args ) )
 //将接收的对象（obj）转换为数组
 $r = get_object_vars( $args );
 elseif ( is_array( $args ) )
 //如果是数组则不转换
 $r =& $args;
 else
 //将接收的字符串转换为数组
 wp_parse_str( $args, $r );
 if ( is_array( $defaults ) )
 return array_merge( $defaults, $r );
 return $r;
}

The get_object_vars function is used to return an associative array composed of object attributes. The

array_merge function is used to merge the cells of two or more arrays, and the values ​​in one array are appended to the previous array. Returns the resulting array.

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