February 11, 2011 
Definition:
function apply_filters($tag, $value) {}
Call the functions added to a filter hook.
The callback functions attached to filter hook $tag are invoked by calling this function. This function can be used to create a new filter hook by simply calling this function with the name of the new hook specified using the $tag parameter.
Parameters
- string $tag: The name of the filter hook.
- mixed $value: The value on which the filters hooked to <tt>$tag</tt> are applied on.
- mixed $var,…: Additional variables passed to the functions hooked to <tt>$tag</tt>.
Return values
returns:The filtered value after all hooked functions are applied to it.
Defined filters
- $tag
apply_filters($tag, $value)
Source code
function apply_filters($tag, $value) {
global $wp_filter, $merged_filters, $wp_current_filter;
$args = array();
// Do 'all' actions first
if ( isset($wp_filter['all']) ) {
$wp_current_filter[] = $tag;
$args = func_get_args();
_wp_call_all_hook($args);
}
if ( !isset($wp_filter[$tag]) ) {
if ( isset($wp_filter['all']) )
array_pop($wp_current_filter);
return $value;
}
if ( !isset($wp_filter['all']) )
$wp_current_filter[] = $tag;
// Sort
if ( !isset( $merged_filters[ $tag ] ) ) {
ksort($wp_filter[$tag]);
$merged_filters[ $tag ] = true;
}
reset( $wp_filter[ $tag ] );
if ( empty($args) )
$args = func_get_args();
do {
foreach( (array) current($wp_filter[$tag]) as $the_ )
if ( !is_null($the_['function']) ){
$args[1] = $value;
$value = call_user_func_array($the_['function'], array_slice($args, 1, (int) $the_['accepted_args']));
}
} while ( next($wp_filter[$tag]) !== false );
array_pop( $wp_current_filter );
return $value;
}
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