Yogesh Chauhan's Blog

apply_filters function in WordPress

in WordPress on February 20, 2021

In this post, we saw the add_filter hook and how to use that to add functions to your WordPress code.

applt_filters calls the functions that have been added to the filter hook.

Even after adding the functions, the job is not done. We need to call those functions. Those functions attached to the filter hook are invoked by calling applt_filters function.


apply_filters($tag, $value )

Where the $tag is required as a string variable — it’s the name of the filter hook.

and the second parameter $value is mixed – these are the values to filter.

We can call applt_filters function to create a new filter hook. To do so, we need to call applt_filters function with the name of the new hook that was specified using the $tag parameter.

Using applt_filters function, we can also pass multiple arguments to hooks.


// The filter callback function.
function concat( $str, $str1, $str2) {
    $str .= $str1 . $str2
    return $str;
add_filter( 'concat_filter', 'concat', 10, 3 );

In the example above, concat_filter is the hook. We apply the filters by calling the concat() function that’s hooked onto concat_filter above. We are passing the additional arguments as $str1 and $str2.

The last two parameters in add_filter, 10 and 3 are very important. 10 is the priority and 3 is the number of the parameters.

Credit: WordPress Developers

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