Read options telephone number and make it international for mobile devices.

click_telephone.php

<?php

   function click_telephone($telephone, $string = null, $prepend = null, $prepend_zero = null) {

        /*
            Parameters:
            $telephone       - string, the actual number
            $string          - string, if you want to dispay a clickable strong rather than telephone number,
            $prepend         - string, prepend the telephone number.
            $countrycode     - string, country code or default UK 0044
        */

        $ori_tel    = str_replace( ' ', '', $telephone );
        $new_tel    = "0044".substr($ori_tel, 1);
        $output     = "<a href='tel:".$new_tel."' class='tel'>";
        
        if( $string ) {$output.=$string;}
        else {
            if($prepend) {
               $output.=$prepend." "; 
            }
            if($prepend_zero == true) {
               $output.="0"; 
            }
            $output.=substr($ori_tel, 1);
        }

        $output     .= "</a>";
        
        return $output;

    }
    
    echo click_telephone( get_field('options_mobile', 'option') );
    or
    echo click_telephone( get_field('options_telephone', 'option'), '<i class="fa fa-phone"></i>', 'UK: +44', true );
    of
    echo click_telephone( get_field('footer_phone_number', 'option'), null, null, null, null );
    
?>