<?phpadd_filter( 'login_errors', 'login_errors_example' );function login_errors_example( $error ) {$error = 'this is the modified error';return $error;
}?>

<?phpadd_filter( 'comment_post_redirect', 'comment_post_redirect_example' );function comment_post_redirect_example( $location ) {return '/thanks-for-your-comment/';
}?>

 1 <?php
 2
 3 add_filter( 'allowed_redirect_hosts', 'allowed_redirect_hosts_example' );
 4
 5 function allowed_redirect_hosts_example( $content ) {
 6     $content[] = 'forum.mywebsite.com';
 7     $content[] = 'welcome.mywebsite.com';
 8     $content[] = 'help.mywebsite.com';
 9     return $content;
10 }
11
12 // Example source: http://codex.wordpress.org/Plugin_API/Filter_Reference/allowed_redirect_hosts
13
14 ?>

 1 <?php
 2
 3 add_filter( 'body_class', 'body_class_example' );
 4
 5 function body_class_example( $classes ) {
 6     if( is_single() ) {
 7         foreach( get_the_category( get_the_ID() ) as $category )
 8             $classes[] = 'cat-' . $category->category_nicename;
 9     }
10     return $classes;
11 }
12
13 // Example source: https://codex.wordpress.org/Function_Reference/body_class#Add_Classes_By_Filters
14
15 ?>

 1 <?php
 2
 3 add_filter( 'locale', 'locale_example' );
 4
 5 function locale_example( $lang ) {
 6     if ( 'tr' == $_GET['language'] ) {
 7         return 'tr_TR';
 8     } else {
 9         return $lang;
10     }
11 }
12
13 // Example source: http://codex.wordpress.org/Plugin_API/Filter_Reference/locale
14
15 ?>

1 <?php
2
3 add_filter( 'sanitize_user', 'strtolower' );
4
5 // Example source: http://codex.wordpress.org/Plugin_API/Filter_Reference/sanitize_user
6
7 ?>

<?phpadd_filter( 'the_content', 'the_content_example' );function the_content_example( $content ) {return preg_replace('/<p>\s*(<a .*>)?\s*(<img .* \/>)\s*(<\/a>)?\s*<\/p>/iU', '\1\2\3', $content);
}// Example source: http://wpsnipp.com/index.php/functions-php/remove-p-tag-from-around-images-in-the_content/?>

 1 <?php
 2
 3 add_filter( 'the_password_form', 'the_password_form_example' );
 4
 5 function the_password_form_example() {
 6     $output  = '<form action="' . esc_url( site_url( 'wp-login.php?action=postpass', 'login_post' ) ) . '" method="post">';
 7     $output .= '<span>' . __( "Enter the password:" ) . ' </span>';
 8     $output .= '<input name="post_password" type="password" size="20" />';
 9     $output .= '<input type="submit" name="Submit" value="' . esc_attr__( "Go" ) . '" />';
10     $output .= '</form>';
11     return $output;
12 }
13
14 // Example source: http://codex.wordpress.org/Using_Password_Protection#Password_Form_Text
15
16 ?>

1 <?php
2
3 add_filter( 'the_terms', 'strip_tags' );
4
5 ?>

<?phpadd_filter( 'wp_mail_from', 'wp_mail_from_example' );function wp_mail_from_example( $email ) {return 'my.email.address@mywebsite.com';
}?>