How To Create WordPress Plugin

To Create WordPress Plugin you need to know how basic php , css and html works.
Here is some function which ussually i used for wordpress plugin.

PREFIX

It’s suggested to prefix your function and variable. For example using mfp (My First Plugin). Here is the example $mfp_string , mfp_function.

DIR and URL

You can detect directory and url WordPress Plugin using function plugin_dir_path( FILE ) and plugin_dir_url( FILE ).
I ussually use constant some constanta like this :

define( 'MFP_DIR' , plugin_dir_path( __FILE__ ) );
define( 'MFP_URL' , plugin_dir_url( __FILE__ ) );

HOOK

Hook is function so you don’t need to change the core code. There are 2 hooks : action and filter.

ACTION

Here are some function which you need to know : do_action , add_action and remove_action

DO_ACTION

For example your index.php in theme like this

<?php
	do_action( 'mfp_header_before' );
	echo '<div>HEADER</div>';
	do_action( 'mfp_header_after' );
	
	do_action( 'mfp_content_before' );
	echo '<div>CONTENT</div>';
	do_action( 'mfp_content_after' );
	
	do_action( 'mfp_footer_before' );
	echo '<div>FOOTER</div>';
	do_action( 'mfp_footer_after' );

?>

ADD_ACTION

You can add action in the plugin without change index.php in the theme. For example :

<?php
	function mfp_example_header_before1() {
		echo '<div>HEADER BEFORE 1</div>';
	}
	add_action( 'mfp_header_before','mfp_example_header_before1' );
	
	function mfp_example_header_before2() {
		echo '<div>HEADER BEFORE 2</div>';
	}
	add_action( 'mfp_header_before','mfp_example_header_before2' );
	
	function mfp_example_footer_before1() {
		echo '<div>FOOTER BEFORE 1</div>';
	}
	add_action( 'mfp_footer_before','mfp_example_footer_before1' );
?>

REMOVE_ACTION

If you want to remove just use for example remove_action( ‘mfp_header_before’,’mfp_example_header_before2′ ); or if you want to remove all action remove_all_actions( ‘mfp_header_before’ );

WORDPRESS ACTION STANDAR WHICH YOU NEED TO KNOW : wp_head , wp_footer

FILTER

Filter is hook for variable. Function which you need to know apply_filters and add_filter.
Example :

<?php
	function mfp_do_filter( $mfp_text ) {
		$mfp_text = "VAR DO FILTER";
		return $mfp_text;
	}
	add_filter( 'mfp_var_filter', 'mfp_do_filter' );
	
	function mfp_apply_filter() {
		$mfp_var = "VAR APPLY FILTER";
		$mfp_var = apply_filters( 'mfp_var_filter' , $mfp_var );
		echo $mfp_var;
	}
	
	mfp_apply_filter();
?>

REMOVE_FILTER

If you want to remove filter. Just use for example remove_filter( ‘mfp_var_filter’ , ‘mfp_do_filter’ ); or if you want ro remove all just use function remove_all_filter( ‘mfp_var_filter’ );

WORDPRESS FILTER WHICH YOU NEED TO KNOW : the_content

After you know some basic functions now it’s time to create your first plugin.
HERE IS SAMPLE FIRST PLUGIN TO INSERT BEFORE AND AFTER CONTENT IN THE POST / PAGE

<?php
/*
Plugin Name: My First Plugin
Plugin URI: http://wpamanuke.com/how-to-create-wordpress-plugin/
Description: First plugin which i made
Version: 1.0
Author: WPAmanuke
Author URI: http://wpamanuke.com
License: GPLv2
*/

function mfp_filter_the_content_before( $content ) {
    $custom_content = '<div>Before Content Filter</div>';
    $custom_content .= $content;
    return $custom_content;
}
add_filter( 'the_content', 'mfp_filter_the_content_before' );

function mfp_filter_the_content_after( $content ) {
    $custom_content = '<div>After Content Filter</div>';
    $custom_content = $content . $custom_content;
    return $custom_content;
}
add_filter( 'the_content', 'mfp_filter_the_content_after' );

?>