Smarty plugin for generating form fields

function.formfield.php

<?php
/* formfield plugin
 * Create dynamic HTML form elements programmatically
 *
 * Parameters:
 * type - the type of element, can be any standard HTML <input> type or one of the options below (default = text)
 * options - for select, checkboxes, and radios types, this should be an associative array of key => label pairs
 * value - the default value of the element; for select or checkboxes types this can be an array selected/checked values, if an array is set for other types, only the first value in the array is used
 * wrapper - the HTML wrapper to be applied to individual elements when using checkboxes or radios, use %s to specify where default makeup should be inserted
 * content - the content between <button> and </button> tags in an htmlbutton field
 * emptyoption - a valueless label for a select list to serve as a default selection
 * all other parameters will be set as attributes to the elements
 * 
 * Element Types:
 *
 * checkboxes - creates a set of checkboxes from an array of options (expects options param, value param may be an array or single value)
 * radios - creates a set of radio buttons from an array of options (expects options param, value param should be a single value)
 * <select> - creates a select box from an array of options (expects options param, value param may be an array or a single value)
 * <textarea> - creates a textarea (value param will be inserted as the inner content to the <textarea> and </textarea> tags)
 * <button> - use type="htmlbutton" to create a <button> element (content param will be inserted as inner content between the <button> and </button> tags)
 * <input> - any other type param will be converted to a standard <input> element with the specified type and all other values added as attributes
 */
function smarty_function_formfield($params, Smarty_Internal_Template $template)
{
    //extract the control variables from the parameters
    $type = _smarty_function_formfield_extractParam($params, 'type', 'text');
    $options = _smarty_function_formfield_extractParam($params, 'options', array());
    $value = _smarty_function_formfield_extractParam($params, 'value', '');
    $wrapper = _smarty_function_formfield_extractParam($params, 'wrapper');
    $content = _smarty_function_formfield_extractParam($params, 'content');

    //normalize the disabled attribute
    if(isset($params['disabled'])) {
        if($params['disabled'] == false) {
            unset($params['disabled']);
        }
        else {
            $params['disabled'] = 'disabled';
        }
    }
    
    //a string to hold the output
    $output = '';
    
    if($type == 'checkboxes') {
        //a set of checkboxes
        
        //make sure value is an array
        $value = (is_array($value)) ? $value : array($value);
        
        //name needs square brackets for PHP to parse it correctly
        $name = _smarty_function_formfield_extractParam($params, 'name', '');
        $name = (!empty($name)) ? 'name="' . $name . '[]"' : '';
        
        //get the id, a number will be appended so that each element has a unique id
        $id = _smarty_function_formfield_extractParam($params,'id');
        
        //store each element in an output array
        $output = array();
        
        $count = 0;
        foreach($options as $key => $label) {
            $chk = (in_array($key, $value)) ? 'checked="checked"' : '';
            
            $myid = (!empty($id)) ? 'id="' . $id . '-' . $count . '"': '';
            
            $html = sprintf('<label><input type="checkbox" %s %s %s value="%s" %s />%s</label>',
                    $name, //field name
                    $myid, //unique id
                    _smarty_function_formfield_getAttribs($params),  //parsed attributes
                    $key, //value
                    $chk, //checked status
                    htmlspecialchars($label, ENT_QUOTES) //label
            );
            
            if(!empty($wrapper)) {
                //wrap the HTML in the wrapper, if specified
                $html = sprintf($wrapper, $html);
            }
            
            //add element to the output array
            $output[] = $html;
            
            $count++;
        }
        
        //collapse output array into a string
        $output = implode("\n", $output);
    }
    else if($type == 'radios') {
        //a set of radio buttons
        
        //value should not be an array
        $value = (is_array($value)) ? array_shift($value) : $value;
        
        //get the id; a sequential number will be appended on each element so that each has a uniqu id
        $id = _smarty_function_formfield_extractParam($params, 'id');
        
        //store each element in an output array
        $output = array();
        
        $count = 0;
        foreach($options as $key => $label) {
            //empty() evals to true for empty string, null, and zero
            //isset() evals to true for empty string
            //strlen() evals to > 0 for anything other than empty string, null 
            $chk = (strlen($value) > 0 && $key == $value) ? 'checked="checked"' : '';
            //$chk = ($key == $value) ? 'checked="checked"' : '';
            
            $myid = (!empty($id)) ? 'id="' . $id . '-' . $count . '"': '';

            $html = sprintf('<label><input type="radio" %s %s value="%s" %s />%s</label>',
                    $myid, //unique id
                    _smarty_function_formfield_getAttribs($params),  //parsed attributes
                    $key, //value
                    $chk, //checked status
                    htmlspecialchars($label, ENT_QUOTES) //label
            );
            
            if(!empty($wrapper)) {
                //wrap the HTML in the wrapper, if specified
                $html = sprintf($wrapper, $html);
            }
            
            //add element to the output array
            $output[] = $html;
            
            $count++;
        }
        
        //collapse output array into a string
        $output = implode("\n", $output);
    }
    else if($type == 'select') {
        //select box
        
        //make sure value is an array
        $value = (is_array($value)) ? $value : array($value);
        unset($params['value']);
        
        //standardize multiple
        $multiple = _smarty_function_formfield_extractParam($params, 'multiple');
        $multiple = (!empty($multiple)) ? 'multiple="multiple"' : '';
        
        //opening tag
        $output = sprintf('<select %s %s>',
            _smarty_function_formfield_getAttribs($params), //parsed attributes
            $multiple //multiple option
        ) . "\n";
        
        //empty option
        $emptyoption = (isset($params['emptyoption'])) ? $params['emptyoption'] : null;
        unset($params['emptyoption']);
        if($emptyoption) {
            $output .= sprintf('  <option value="">%s</option>', htmlspecialchars($emptyoption, ENT_QUOTES)) . "\n";
        }
        
        //actual options
        foreach($options as $key => $label) {
            $sel = (in_array($key, $value)) ? 'selected="selected"' : '';
            
            $output .= sprintf('  <option value="%s" %s>%s</option>',
                    $key, //option value
                    $sel, //selection status
                    htmlspecialchars($label, ENT_QUOTES) //label
            ) . "\n";
        }
        
        //closing tag
        $output .= '</select>';       
    }
    else if($type == 'textarea') {
        //textarea
        
        //value should not be an array
        $value = (is_array($value)) ? array_shift($value) : $value;
        
        $output = sprintf('<textarea %s>%s</textarea>',
                _smarty_function_formfield_getAttribs($params), //parsed attributes
                htmlspecialchars($value, ENT_QUOTES)  //value
        ); 
    }
    else if($type == 'htmlbutton') {
        //value should not be an array
        $value = (is_array($value)) ? array_shift($value) : $value;
        $value = (!empty($value)) ? 'value="' . htmlspecialchars($values, ENT_QUOTES) . '"' : '';
        
        $output = sprintf('<button %s %s>%s</button>',
                _smarty_function_formfield_getAttribs($params), //parsed attributes
                $value, //element value
                htmlspecialchars($content, ENT_QUOTES) //the tags inner content
        );
    }
    else {
        //standard <input> element
        //works with all other elements including HTML5 form elements as well as single checkboxes and radio buttons
        
        //value should not be an array
        $value = (is_array($value)) ? array_shift($value) : $value;
        $value = ($value != '') ? 'value="' . htmlspecialchars($value, ENT_QUOTES) . '"' : '';
        
        $output = sprintf('<input type="%s" %s %s />',
                $type,  //field type
                _smarty_function_formfield_getAttribs($params), //parsed attributes
                $value //field value
        );
    }
    
    return $output;
}

/*
 * find a value in an associative array by key, remove the element from the array, and return the value
 * optionally, a default value can be specified if the requested key does not exist, otherwise null will be returned
 */
function _smarty_function_formfield_extractParam(&$params, $paramName, $default=null)
{   
    $paramVal = $default;
    
    if(isset($params[$paramName])) {
        $paramVal = $params[$paramName];
    }
    
    unset($params[$paramName]);
    
    return $paramVal;
}

/*
 * convert an associative array into a set of HTML attributes
 */
function _smarty_function_formfield_getAttribs($params)
{
    //output array
    $output = array();
    
    foreach($params as $key => $value) {
        $output[] = sprintf('%s="%s"', $key, htmlspecialchars($value, ENT_QUOTES));
    }
    
    //return output as a string
    return implode(' ', $output);
}