Hook different functions to the same filter conditionally OR Pass additional arguments to existing filter?

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Is it possible to hook 3 different functions to the same filter conditionally, like:

<?php
if(a){
    add_filter('the_content', 'fnc_1');
}
else if(b){
    add_filter('the_content', 'fnc_2');
}
else{
    add_filter('the_content', 'fnc_3');
}
?>

Or if this isn’t possible, then can I pass an additional argument to the same function to flag my 3 different conditions? Something like:

<?php
if(a){
    add_filter('the_content', 'fnc_1', 'condition_a');
}
else if(b){
    add_filter('the_content', 'fnc_1', 'condition_b');
}
else{
    add_filter('the_content', 'fnc_1', 'condition_c');
}
?>

All I could find from my reading is that it has to do something with apply_filters, but couldn’t get around it.

Please can anyone tell me how to achieve this?
Thanks!

1 Answer
1

Since it does appear to be an interesting question, I’ll go ahead an compile an answer.

Method 1

Totally fine, will work. Here’s the compact piece of code I used to test it:

function fnc_1( $content ) { return 'func1 :: '.$content;   }
function fnc_2( $content ) { return 'func2 :: '.$content;   }
function fnc_3( $content ) { return 'func3 :: '.$content;   }

$a = false;
$b = false;

if ( $a ) add_filter( 'the_content', 'fnc_1' );
elseif ( $b ) add_filter( 'the_content', 'fnc_2' );
else add_filter( 'the_content', 'fnc_3' );

Method 2

add_filter does not allow you to pass additional arguments to the filter function, but if you really need to share one function you can wrap a custom filter around the filter like so:

add_filter( 'wpse31470_filter_wrapper', 'wpse31470_filter_wrapper_func', null, 2 );

function wpse31470_filter_wrapper_func( $content, $condition ) {
    if ( $condition ) return 'TRUE :: '.$content;
    else return 'FALSE ::'.$content;
}

add_filter( 'the_content', 'wpse31470_the_content_filter' );
function wpse31470_the_content_filter( $content ) {
    $condition = true;
    return apply_filters( 'wpse31470_filter_wrapper', $content, $condition );
}

The purpose of the wpse31470_the_content_filter is to wrap the argument supplied by the_content filter and pass it on to your own wpse31470_filter_wrapper along with any additional arguments.

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