详解WordPress中创建和添加过滤器的相关PHP函数

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详解WordPress中创建和添加过滤器的相关PHP函数_php技巧

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May 16, 2016 pm 08:01 PM

wordpress filter

apply_filters()（创建过滤器）
apply_filters() 函数用来创建一个过滤器，大多数被用在函数中，是 WordPress 插件机制中非常重要的一个函数，能让其它的主题和插件对一个值进行修改过滤。

用法

1	`apply_filters(` `$tag,` `$value,` `$var... );`

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参数

$tag

（字符串）（必须）过滤器的名字。

默认值：None

$value

（混合）（必须）要过滤的值，如果没人过滤则直接返回这个值。

$var

（混合）（可选）传给过滤函数额外的变量参数，辅助过滤函数对返回值进行操作，可以添加无限个。

返回值

（混合）过滤后的值，如果没人过滤则直接返回 $value 的值。

例子

没人过滤：

1	`echo` `apply_filters(` `'test',` `'可以被修改的值'` `);`

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打印结果：

可以被修改的值

有人过滤：

function test_func(){
  return '修改值';
}
add_filter( 'test', 'test_func' );
echo apply_filters( 'test', '可以被修改的值' );

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打印结果：

修改值

接收参数：

function test_func(){
  return '修改值';
}
add_filter( 'test', 'test_func' );
function test_func2( $text ){
  return $text . '2';
}
add_filter( 'test', 'test_func2' );
echo apply_filters( 'test', '可以被修改的值' );

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多个参数：

function test_func( $text, $var, $var2 ){
  return '修改值' . $var1 . $var2;
}
add_action( 'test', 'test_func', 10, 3 );
echo apply_filters( 'test', '可以被修改的值', '辅助值1', '辅助值2' );

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其它

此函数位于：wp-includes/plugin.php

add_filter()（添加过滤器）
add_filter() 可以挂载一个函数到指定的过滤器上。

用法

1	`add_filter(` `$tag,` `$function_to_add,` `$priority,` `$accepted_args` `);`

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参数

$tag

（字符串）（必须）所挂载的过滤器名字（和目标 apply_filters() 函数的 $tag 属性一样）。

默认值：None

$function_to_add

（回调）（必须）要挂载的回调函数，参考 PHP 回调函数类型文档。

默认值：None

$priority

（整数）（可选）执行顺序，越小函数越先被执行。

默认值：10

$accepted_args

（整数）（可选）回调函数接收的参数数量，设置多个可以接收更多 apply_filters() 函数传进来的参数。

默认值：1

返回值

（布尔）总是 True

例子

function test_func( $text, $var1, $var2 ){
  return $text . $var1 . $var2;
}
add_action( 'test', 'test_func', 10, 3 );
echo apply_filters( 'test', '参数2', '参数3', '参数4' );

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打印：

test参数2参数3

其它

该函数位于：wp-includes/plugin.php

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