How to translate NinjaForms labels

NinjaForms is already translated to several languages, but as soon as you save the message labels your entries are saved as static text.

WPML String Translation

I tried to translate the labels with WPMLs string translation feature. WPML finds the labels, allows translation, but doesn’t display the changes in frontend.

I had a look at the NinjaForms source code and found a general flexible solution.

NinjaForms Filters

NinjaForms uses filters for each of the labels so we can override every field value in our code and of course allow the values to be translated.

To even simplify this step I don’t use own translations but the contained translations from NinjaForms.  For future projects I’ll just copy these lines to the functions file and my labels are already translated to all available languages.

add_filter( 'ninja_forms_labels/date_format', 
    function(){ return  'd.m.Y'; } 
);

add_filter( 'ninja_forms_labels/currency_symbol', 
    function(){ return  '€'; } 
);

add_filter( 'ninja_forms_labels/req_div_label', 
    function(){ return  sprintf( __( 'Fields marked with an %s*%s are required', 'ninja-forms' ), '<span class="ninja-forms-req-symbol">','</span>' ); } 
);

add_filter( 'ninja_forms_labels/req_field_symbol', 
    function(){ return  '<strong>*</strong>'; } 
);

add_filter( 'ninja_forms_labels/req_error_label', 
    function(){ return  __( 'Please ensure all required fields are completed.', 'ninja-forms' ); } 
);

add_filter( 'ninja_forms_labels/req_field_error', 
    function(){ return  __( 'This is a required field', 'ninja-forms' ); } 
);

add_filter( 'ninja_forms_labels/spam_error', 
    function(){ return  __( 'Please answer the anti-spam question correctly.', 'ninja-forms' ); } 
);

add_filter( 'ninja_forms_labels/honeypot_error', 
    function(){ return  __( 'Please leave the spam field blank.', 'ninja-forms' ); } 
);

add_filter( 'ninja_forms_labels/timed_submit_error', 
    function(){ return  __( 'Please wait to submit the form.', 'ninja-forms' ); } 
);

add_filter( 'ninja_forms_labels/javascript_error', 
    function(){ return  __( 'You cannot submit the form without Javascript enabled.', 'ninja-forms' ); } 
);

add_filter( 'ninja_forms_labels/invalid_email', 
    function(){ return  __( 'Please enter a valid email address.', 'ninja-forms' ); } 
);

add_filter( 'ninja_forms_labels/process_label', 
    function(){ return  __( 'Processing', 'ninja-forms' ); } 
);

add_filter( 'ninja_forms_labels/password_mismatch', 
    function(){ return  __( 'The passwords provided do not match.', 'ninja-forms' ); } 
);