I want to run a function after the wp(); line in the file wp-blog-header.php, what is the proper hook to use here?

<?php
/**
 * Loads the WordPress environment and template.
 *
 * @package WordPress
 */

if ( !isset($wp_did_header) ) {

    $wp_did_header = true;

    // Load the WordPress library.
    require_once( dirname(__FILE__) . '/wp-load.php' );

    // Set up the WordPress query.
    wp();

    /********************************************
       I WANT TO RUN THE FUNCTION AT THIS POINT 
     ********************************************/

    // Load the theme template.
    require_once( ABSPATH . WPINC . '/template-loader.php' );

}

Why do I need the hook

We are migrating to a new website and we have to care about the old URLs, so what I did:

1. Added the following rewrite rule to our NGINX config file:

rewrite \D+(\/\d+\/\D+)$ /index.php?redirect=$1 break;

This rule will add an extra parameter redirect to the URL (old URL) with a value that I will be using to get the new final URL.

2. Then I will run the following code to get this value from the incoming URL and get the final URL by querying a 2-columns table that maps each value redirect_from with a final URL redirect_to:

/**
 * 1. Check if the URL has a parameter [redirect]
 * 2. If NO, proceed to the next step
 * 3. If YES, then get that parameter value and look into [redirects] table
 * 4. If you found a row that has that value, then get the [redirect_to] value
 * 5. Redirect to that URL [redirect_to]
 */

if (isset($_GET['redirect'])) {
    // Get the parameter value from the URL
    $redirect_from = $_GET['redirect'];
    // Add the table prefix to the table name
    $table_name = $wpdb->prefix . 'redirects';
    // The SQL query
    $query = "
        SELECT redirect_to
        FROM $table_name
        WHERE redirect_from = '$redirect_from';
    ";
    // Run the SQL query and get the results
    $result = $wpdb->get_results($query, OBJECT);

    // If there was a result then do the redirection and exit
    if (wp_redirect($result[0]->redirect_to)) {exit;}
}

Note: No way to get the new URLs from old URLs, here is an example of the old and new URLs:

Redirect from:

to:

I want to run a function after the wp(); line in the file wp-blog-header.php, what is the proper hook to use here?

<?php
/**
 * Loads the WordPress environment and template.
 *
 * @package WordPress
 */

if ( !isset($wp_did_header) ) {

    $wp_did_header = true;

    // Load the WordPress library.
    require_once( dirname(__FILE__) . '/wp-load.php' );

    // Set up the WordPress query.
    wp();

    /********************************************
       I WANT TO RUN THE FUNCTION AT THIS POINT 
     ********************************************/

    // Load the theme template.
    require_once( ABSPATH . WPINC . '/template-loader.php' );

}

Why do I need the hook

We are migrating to a new website and we have to care about the old URLs, so what I did:

1. Added the following rewrite rule to our NGINX config file:

rewrite \D+(\/\d+\/\D+)$ /index.php?redirect=$1 break;

This rule will add an extra parameter redirect to the URL (old URL) with a value that I will be using to get the new final URL.

2. Then I will run the following code to get this value from the incoming URL and get the final URL by querying a 2-columns table that maps each value redirect_from with a final URL redirect_to:

/**
 * 1. Check if the URL has a parameter [redirect]
 * 2. If NO, proceed to the next step
 * 3. If YES, then get that parameter value and look into [redirects] table
 * 4. If you found a row that has that value, then get the [redirect_to] value
 * 5. Redirect to that URL [redirect_to]
 */

if (isset($_GET['redirect'])) {
    // Get the parameter value from the URL
    $redirect_from = $_GET['redirect'];
    // Add the table prefix to the table name
    $table_name = $wpdb->prefix . 'redirects';
    // The SQL query
    $query = "
        SELECT redirect_to
        FROM $table_name
        WHERE redirect_from = '$redirect_from';
    ";
    // Run the SQL query and get the results
    $result = $wpdb->get_results($query, OBJECT);

    // If there was a result then do the redirection and exit
    if (wp_redirect($result[0]->redirect_to)) {exit;}
}

Note: No way to get the new URLs from old URLs, here is an example of the old and new URLs:

Redirect from:

http://www.example/category/sub-category/post-id/slug

to:

https://www.example/category/sub-category/yyyy/mm/dd/slug

• hooks
• actions
• wp-blog-header.php

• There’s lots of hooks that run at various places after that. What exactly do you want to do? – Jacob Peattie Commented Mar 16, 2019 at 14:48
• Thank you @JacobPeattie , I've already updated the question, I appreciate any help. – Jaafar Abazid Commented Mar 16, 2019 at 15:24

2 Answers 2

The appropriate hook for handling redirects would be template_redirect:

function wpse_331804_redirects() {
    /**
     * 1. Check if the URL has a parameter [redirect]
     * 2. If NO, proceed to the next step
     * 3. If YES, then get that parameter value and look into [redirects] table
     * 4. If you found a row that has that value, then get the [redirect_to] value
     * 5. Redirect to that URL [redirect_to]
     */

    if (isset($_GET['redirect'])) {
        // Get the parameter value from the URL
        $redirect_from = $_GET['redirect'];
        // Add the table prefix to the table name
        $table_name = $wpdb->prefix . 'redirects';
        // The SQL query
        $query = "
            SELECT redirect_to
            FROM $table_name
            WHERE redirect_from = '$redirect_from';
        ";
        // Run the SQL query and get the results
        $result = $wpdb->get_results($query, OBJECT);

        // If there was a result then do the redirection and exit
        if (wp_redirect($result[0]->redirect_to)) {exit;}
    }
}
add_action( 'template_redirect', 'wpse_331804_redirects' );

Perhaps you could put your redirect function into a must-use plugin and hook the function to muplugins_loaded. $wpdb should be available then and I think it would minimize the amount of code loaded in the case a redirect is needed.

You can also have a look at the action reference https://codex.wordpress/Plugin_API/Action_Reference to find other hooks.