An overview of basic fundamental php debugging concepts meant to be accompanied by real world examples on a live or local web server

1. PHP DEBUGGING
BEYOND ECHO

2. PHP MESSAGE TYPES
• Notice – not a best coding practice
• Warning – will probably cause errors upon execution
• Error – fatal (crash)
• Occur when script is interpreted (no execution - e.g., “The white screen of death”), or
at script execution (run-time error halts execution)

3. COMMON PHP ERROR LEVELS
Referenced by constants representing bit level integers to the interpreter
• E_ERROR – fatal run-time error (crash)
• E_WARNING – run-time warning
• E_NOTICE – run-time notice
• E_STRICT – interpretation-time notice
• E_DEPRECATED – run-time – will not work in future PHP versions
• E_ALL – all notices, warnings, and errors

4. DISPLAYING ERRORS
• error_reporting – sets level via constant
• Default: all except E_NOTICE
• display_errors – displays error to users (only use in development environment)
• 1 or 0 – default is 1

6. SCRIPT LEVEL ERROR MANAGEMENT

7. LOGGING ERRORS
• log_errors – toggle error logging
• Default: off
• log_errors_max_len – length of error message in bytes
• default: 1024
• 0 is unlimited
• error_log – full path to log file
• default: NULL (goes to server error log; not a best practice)
• set log file path outside of the web root

8. DISPLAYING ERRORS
• error_reporting – sets level via constant
• Default: all except E_NOTICE
• display_errors – displays error to users (only use in development environment)
• 1 or 0 – default is 1

9. TRIGGER_ERROR

10. DEBUG_BACKTRACE
• backtrace – sequence of function/method calls
• invaluable in debugging frameworks/complex structures
• returns associative array – keyed in ascending order
• lowest number - last execution
• each contains function/method, line number, file, class, object, and arguments!