shortcode

shortcode.php

<?php

function callout_shortcode( $atts ) {
	$out    = '';
	$atts  = shortcode_atts(
		array(
			'callout_h4' => 'This is a header',
			'callout_p'  => 'This is the paragraph below it',
		),
		$atts
	);

	$out .= '<div class="callout">';
	$out .= '<h4>' . esc_html( $atts['callout_h4'] ) . '</h4>';
	$out .= '<p>' . esc_html( $atts['callout_p'] ) . '</p>';
	$out .= '</div>';

	return $out;
}

add_shortcode( 'callout', 'callout_shortcode' );