change in font size and line spacing between two sentences

certificate_text = str_replace('[name]', '[name]', $certificate[0]->certificate_text);
$certificate[0]->certificate_text = str_replace('[present_address]', '[current_address]', $certificate[0]->certificate_text);
$certificate[0]->certificate_text = str_replace('[guardian]', '[guardian_name]', $certificate[0]->certificate_text);
$certificate[0]->certificate_text = str_replace('[phone]', '[mobileno]', $certificate[0]->certificate_text);
foreach ($students as $student) {
$certificate_body = "";
$certificate_body = $certificate[0]->certificate_text;
foreach ($student as $std_key => $std_value) {
if ($std_key == "dob") {
if ($std_value != "0000-00-00" && $std_value != "") {
$std_value = date($this->customlib->getSchoolDateFormat(), $this->customlib->dateYYYYMMDDtoStrtotime($std_value));
}
}
if ($std_key == "admission_date") {
if ($std_value != "0000-00-00" && $std_value != "") {
$std_value = date($this->customlib->getSchoolDateFormat(), $this->customlib->dateYYYYMMDDtoStrtotime($std_value));
}
}
if ($std_key == "created_at") {
if ($std_value != "0000-00-00" && $std_value != "") {
$std_value = date($this->customlib->getSchoolDateFormat(), $this->customlib->dateYYYYMMDDtoStrtotime($std_value));
}
}
$certificate_body = str_replace('[' . $std_key . ']', $std_value, $certificate_body);
}
?>

background_image)) { ?>


content_width . "px" ?>">


enable_student_image == 1) { ?>
enable_image_height . "px" ?>;" src="image); ?>" width="100" height="auto">



header_height . "px" ?>">left_header ?>
header_height . "px" ?>">center_header ?>
header_height . "px" ?>">right_header ?>


content_height . "px" ?>">



footer_height . "px" ?>">left_footer ?>
footer_height . "px" ?>">center_footer ?>
footer_height . "px" ?>">right_footer ?>

this is my code can anyone tell me how to increase font size and style and also space between two sentence