How to call a function within a class method property?

Question

I am trying to call an external function within a class method property. It actually does gets called but at the end of the page and whatever is inside the method property, remains separate.

Since I am a self taught student, it is recent that I have started learning PHP classes so I am not really sure if this can be done or not.

Please guide me how this can be done correctly or if not, then what could be the workaround?

The class I have written is as follows: It will take the input from user while creating of instance and render a modal box based on the input and options selected.

class modalBox{
        private $modal_id, $modal_anim, $header_title, $modal_content,$footer;
        private $headerOpt,$titleOpt,$footerOpt,$closeBtn;

        public function setID($id){
            $this->modal_id = $id;
        }

        public function getID(){
            $modal_id = $this->modal_id;
            return $modal_id;
        }
        public function setTitle($title){
            $this->header_title = $title;
        }

        public function getTitle(){
            $title = $this->header_title;
            return $title;
        }

        public function setBodyContent($content){
            $this->modal_content = $content;
        }

        public function getBodyContent(){
            $modalContent = $this->modal_content;
            return $modalContent;
        }

        public function setFooterContent($footer){
            $this->footer = $footer;
        }

        public function getFooterContent(){
            $footerContent = $this->footer;
            return $footerContent;
        }

        public function initiateModal($modal_anim, $headerOpt, $titleOpt, $closeX, $footerOpt, $footerCloseBtn){ ?>

            <div class="modal <?php if($modal_anim != 'false'){echo $modal_anim;} ?>" id="<?php echo $this->getID(); ?>" style="z-index: 2;"> 
                <div class='modal-dialog'>
                    <div class='modal-content'>
                        <?php
                            // display if header option is set to true
                            if ($headerOpt){
                        ?>
                            <div class="modal-header">
                            <h4><?php echo $this->getTitle(); ?></h4>
                            <?php
                                // display if close button (X) is set to true
                                if($closeX){
                            ?> <button type="button" class="close" data-dismiss="modal">&times;</button> <?php } ?>
                            </div>
                        <?php } ?>
                            <div class="modal-body"><?php echo $this->getBodyContent(); ?></div>
                        <?php if($footerOpt){ ?>
                            <div class="modal-footer"><?php echo $this->getFooterContent(); ?>
                            <?php if($footerCloseBtn){ ?>
                                <button type="button" class="btn btn-danger" data-dismiss="modal">Cancel</button>
                            <?php } ?>
                            </div>
                        <?php } ?>
                    </div>
                </div>
            </div>
        <?php
        }
    }
?>

The function I am trying to call within property is as follows; This function is not inside a class. This is present independently in functions.php which I have included in index file.

function getDocNameList() {
        global $db;
        $getDoc = $db->prepare("SELECT id,doc_name from doctor");
        $getDoc->execute();
        while($docName = $getDoc->fetch(PDO::FETCH_ASSOC)){

// print the returned rows in options list of <select>
            echo "<option value='".$docName['id']."'>".$docName['doc_name']."</option>";
        }
    }

The initiation of class instance is as follows, Please note where I am calling the function

// create class instance
            $rangeModal = new modalBox;

            //set the modal id
            $rangeModal->setID ("rangeFields");

            //set the modal title in header
            $rangeModal->setTitle("Select Date Range");

            // set the body content
            $rangeModal->setBodyContent("
                <form method='post' action='expenditure.php'>
                    <div role='wrapper' class='input-group mb-3'>
                        <input id='datepicker1' name='exp_date_from' value='From Date' required/>
                    </div>
                    <div role='wrapper' class='input-group mb-3'>
                        <input id='datepicker2' name='exp_date_to' value='To Date' required/>
                    </div>
                    <div role='wrapper' class='input-group mb-3'>
                        <select>" . getDocNameList() . "</select>
                    </div>

            ");

            //set the footer content
            $rangeModal->setFooterContent("
                <input type='submit' class='btn btn-success' name='submitRange' />
                </form>
            ");

            /*
            *   @args ---
            *   modal animation
            *   modal header (boolean)
            *   modal title (boolean)
            *   modal close X (boolean)
            *   modal footer (boolean)
            *   modal footer close button (boolean)
            */

            // initiate modal
            $rangeModal->initiateModal('fade',true,true,true,true,true);

I expect the output of the function to be displayed as .... within the block but instead it gets rendered at the bottom of the page just before tag.

Answer 1

You echo it here, so it will be displayed immediately:

echo "<option value='".$docName['id']."'>".$docName['doc_name']."</option>";

So it is not concatenated here, the function does not return anything:

<select>" . getDocNameList() . "</select>

Build it and return it instead:

$output = '';

while($docName = $getDoc->fetch(PDO::FETCH_ASSOC)){
    $output .= "<option value='".$docName['id']."'>".$docName['doc_name']."</option>";
}
return $output;

Or build an array and join the elements:

while($docName = $getDoc->fetch(PDO::FETCH_ASSOC)){
    $output[] = "<option value='".$docName['id']."'>".$docName['doc_name']."</option>";
}
return implode($output);