gform_pre_render

add_filter( 'gform_pre_render', 'your_function_name' );

add_filter( 'gform_pre_render_6', 'your_function_name' );

add_filter( 'gform_pre_render', 'populate_choices' );

//Note: when changing choice values, we also need to use the gform_pre_validation so that the new values are available when validating the field.
add_filter( 'gform_pre_validation', 'populate_choices' );

//Note: when changing choice values, we also need to use the gform_admin_pre_render so that the right values are displayed when editing the entry.
add_filter( 'gform_admin_pre_render', 'populate_choices' );

//Note: this will allow for the labels to be used during the submission process in case values are enabled
add_filter( 'gform_pre_submission_filter', 'populate_choices' );
function populate_choices( $form ) {

    //only populating drop down for form id 5
    if ( rgar( $form, 'id' ) != 5 ) {
       return $form;
    }

    //Reading posts for "Business" category;
    $posts = get_posts( 'category=' . get_cat_ID( 'Business' ) );

    //Creating item array.
    $items = array();

    //Add a placeholder to field id 8, is not used with multi-select or radio, will overwrite placeholder set in form editor.
    //Replace 8 with your actual field id.
    $fields = $form['fields'];
    foreach( $form['fields'] as &$field ) {
      if ( $field->id == 8 ) {
        $field->placeholder = 'This is my placeholder';
      }
    }

    //Adding post titles to the items array
    foreach ( $posts as $post ) {
        $items[] = array( 'value' => $post->post_title, 'text' => $post->post_title );
    }

    //Adding items to field id 8. Replace 8 with your actual field id. You can get the field id by looking at the input name in the markup.
    foreach ( $form['fields'] as &$field ) {
        if ( $field->id == 8 ) {
            $field->choices = $items;
        }
    }

    return $form;
}

// NOTE: update the '221' to the ID of your form
add_filter( 'gform_pre_render_221', 'populate_checkbox' );
add_filter( 'gform_pre_validation_221', 'populate_checkbox' );
add_filter( 'gform_pre_submission_filter_221', 'populate_checkbox' );
add_filter( 'gform_admin_pre_render_221', 'populate_checkbox' );
function populate_checkbox( $form ) {
	if ( empty( $form['id'] ) ) {
		return $form;
	}

    foreach( $form['fields'] as &$field )  {

        //NOTE: replace 3 with your checkbox field id
        $field_id = 3;
        if ( $field->id != $field_id ) {
            continue;
        }

        // you can add additional parameters here to alter the posts that are retreieved
        // more info: http://codex.wordpress.org/Template_Tags/get_posts
        $posts = get_posts( 'numberposts=-1&post_status=publish' );

        $input_id = 1;
        foreach( $posts as $post ) {

            //skipping index that are multiples of 10 (multiples of 10 create problems as the input IDs)
            if ( $input_id % 10 == 0 ) {
                $input_id++;
            }

            $choices[] = array( 'text' => $post->post_title, 'value' => $post->post_title );
            $inputs[] = array( 'label' => $post->post_title, 'id' => "{$field_id}.{$input_id}" );

            $input_id++;
        }

        $field->choices = $choices;
        $field->inputs = $inputs;

    }

    return $form;
}

add_filter( 'gform_pre_render_81', 'populate_html' );
function populate_html( $form ) {
	if ( empty( $form['id'] ) ) {
		return $form;
	}

	//this is a 2-page form with the data from page one being displayed in an html field on page 2
	$current_page = GFFormDisplay::get_current_page( $form['id'] );
	$html_content = "The information you have submitted is as follows:<br/><ul>";
	if ( $current_page == 2 ) {
		foreach ( $form['fields'] as &$field ) {
			//gather form data to save into html field (id 6 on my form), exclude page break
			if ( $field->id != 6 && $field->type != 'page' ) {
				//see if this is a complex field (will have inputs)
				if ( is_array( $field->inputs ) ) {
					//this is a complex fieldset (name, adress, etc.) - get individual field info
					//get field's label and put individual input information in a comma-delimited list
					$html_content .= '<li>' .$field->label . ' - ';
					$num_in_array = count( $field->inputs );
					$counter = 0;
					foreach ( $field->inputs as $input ) {
						$counter++;
						//get name of individual field, replace period with underscore when pulling from post
						$input_name = 'input_' . str_replace( '.', '_', $input['id'] );
						$value = rgpost( $input_name );
						$html_content .= $input['label'] . ': ' . $value;
						if ( $counter < $num_in_array ) {
							$html_content .= ', ';
						}
					}
					$html_content .= "</li>";
				} else {
					//this can be changed to be a switch statement if you need to handle each field type differently
					//get the filename of file uploaded or post image uploaded
					if ( $field->type == 'fileupload' || $field->type == 'post_image' ) {
						$input_name = 'input_' . $field->id;
						//before final submission, the image is stored in a temporary directory
						//if displaying image in the html, point the img tag to the temporary location
						$temp_filename = RGFormsModel::get_temp_filename( $form['id'], $input_name );
						$uploaded_name = $temp_filename['uploaded_filename'];
						$temp_location = RGFormsModel::get_upload_url( $form['id'] ) . '/tmp/' . $temp_filename['temp_filename'];
						if ( !empty( $uploaded_name ) ) {
							$html_content .= '<li>' . $field->label . ': ' . $uploaded_name . "<img src='" . $temp_location . "' height='200' width='200'></img></li>";
						}
					} else {
						//get the label and then get the posted data for the field (this works for simple fields only - not the field groups like name and address)
						$field_data = rgpost('input_' . $field->id );
						if ( is_array( $field_data ) ){
							//if data is an array, get individual input info
							$html_content .= '<li>' . $field->label . ': ';
							$num_in_array = count( $field_data );
							$counter = 0;
							foreach ( $field_data as $data ) {
								$counter++;
								$html_content .= print_r( $data, true );
								if ( $counter < $num_in_array ) {
									$html_content .= ', ';
								}
							}
							$html_content .= '</li>';
						}
						else {
							$html_content .= '<li>' . $field->label . ': ' . $field_data . '</li>';
						}
					}
				}
			}
		}
		$html_content .= '</ul>';
		//loop back through form fields to get html field (id 6 on my form) that we are populating with the data gathered above
		foreach( $form['fields'] as &$field ) {
			//get html field
			if ( $field->id == 6 ) {
				//set the field content to the html
				$field->content = $html_content;
			}
		}
	}
	//return altered form so changes are displayed
	return $form;
}

add_filter( 'gform_pre_render', 'set_conditional_logic' );
add_filter( 'gform_pre_process', 'set_conditional_logic' );
function set_conditional_logic( $form ) {

	//Set conditional logic only for form 14
	if ( rgar( $form, 'id' ) !== 14 ) {
		return $form;
	}

	foreach ( $form['fields'] as &$field ) {
		if ( $field->id == 2 ) {
			$field->conditionalLogic =
				array(
					'actionType' => 'show',
					'logicType' => 'all',
					'rules' =>
						array( array( 'fieldId' => 1, 'operator' => 'is', 'value' => 'First Choice' ) )
				);
		}
	}
	return $form;
}

add_filter( 'gform_pre_render_160', function ( $form ) {
	if ( empty( $form['id'] ) ) {
		return $form;
	}

	$form_id = $form['id'];
	if ( empty( $_POST[ 'is_submit_' . $form_id ] ) && function_exists( 'gf_coupons' ) ) {
		// Define a comma separated string of coupon codes to apply.
		$coupon_codes = '25OFF';

		// Get the specified coupons.
		$coupons = gf_coupons()->get_coupons_by_codes( $coupon_codes, $form );

		// Initialize the $coupon_details array.
		$coupon_details = array();

		// Add the coupons to the $coupon_details array.
		foreach ( $coupons as $coupon ) {
			$coupon_details[ $coupon['code'] ] = $coupon;
		}

		// Add the coupon codes to the hidden coupon codes input for field 3.
		$_POST['input_3'] = $coupon_codes;

		// Add the coupon details to the hidden coupon details input for the form.
		$_POST[ 'gf_coupons_' . $form_id ] = json_encode( $coupon_details );
	}

	return $form;
} );