Tutorials for Developers & Sysadmins
Step-by-step guides for the work we actually do — Laravel, PHP, WordPress, MySQL, Linux servers, and the occasional rabbit hole. Every command has been run on a real machine; nothing is theoretical.
How to Combine Multiple Columns into One String in MySQL
MySQL combine columns into string with CONCAT or CONCAT_WS. NULL-skipping behavior, indexing/performance considerations, and using it from Laravel/WordPress.
How to Check Which MySQL Database or User Is Using the Most CPU
MySQL top CPU usage: SHOW FULL PROCESSLIST for a snapshot, performance_schema for historical digest. Match user/db to sites, then EXPLAIN…
How to Troubleshoot MariaDB Not Starting
MariaDB not starting? Six-step triage: journalctl, MariaDB log file, config validation, port conflict check, disk space, stale PID/socket cleanup. Plus…
How to Restart the MariaDB Server on Linux
MariaDB restart on Linux: sudo systemctl restart mariadb. Covers mysql/mysqld service names, reload vs restart, and verification with systemctl status…
How to Remove a Specific String from a Column in MySQL
MySQL remove string from column: REPLACE for literal strings, REGEXP_REPLACE for patterns. Preview workflow, case sensitivity, and always-back-up warnings.
How to Extract Only the Digits from a String in MySQL
MySQL extract digits from string with REGEXP_REPLACE and [^0-9]. Covers negative/decimal preservation, in-place UPDATE, generated columns, and MySQL 5.7 workarounds.
How to Remove Checkout Fields in WooCommerce
WooCommerce remove checkout fields via woocommerce_checkout_fields filter + unset. Complete field map, the 'always return' gotcha, and which fields to…
How to Include SKU in WooCommerce Search
WooCommerce SKU search: posts_search filter injects meta-queried product IDs into WordPress's core search SQL. Covers scoping, brittleness, and when to…
How to Get the Customer ID from an Order ID in WooCommerce
WooCommerce get customer ID from order: $order->get_user_id() works on HPOS + legacy. Why get_post_meta _customer_user is gone, order snapshot vs…
How to Dynamically Change Currency in WooCommerce
WooCommerce currency switcher in functions.php: validate $_GET against allow-list, cookie for persistence, woocommerce_currency filter to apply. Conversion caveat.