How to debug php

How to debug a PHP program?

1. Check whether there are syntax errors

php -l test.php

2. Basic debugging

Basic debugging API:

var_dump($var);print_r($var);echo $var;

Basic configuration:

display_errors、log_errors、error_reporting、error_log

Note: Sometimes, error reporting will be turned off , needs to be turned on manually.

Commonly used codes:

ini_set("display_errors","On");
error_reporting(E_ALL);

3. Use the error collection function

debug_backtrace —Generate a backtrace ( backtrace)

debug_print_backtrace — Print a backtrace.

error_clear_last — Clear the latest error

error_get_last — Get the last error that occurred

error_log — Send error information to somewhere

error_reporting — Set what kind of PHP errors should be reported

restore_error_handler — Restore the previous error handling function

restore_exception_handler — Restore the previously defined exception handling function.

set_error_handler — Set a user-defined error handling function

set_exception_handler — Set a user-defined exception handling function

trigger_error — Generates a user-level error/warning/notice message

user_error — Alias ​​for trigger_error

register_shutdown_function('my_shutdown_handler');

function my_shutdown_handler()
{
    $error = error_get_last();
    if ($error) {
        try{
            //发送邮件
        } catch(Exception $e) {

        }
    }
    return false;
}

4. Remember log

file_put_contents('log.text', var_export($var, 1), FILE_APPEND);

In addition, you also need to configure error_log

Generally, check the error log of apache. Command line execution errors cannot be collected.

5. Use xdebug tool

xdebug_start_trace();
/* 业务代码 */
xdebug_stop_trace();

Recommended tutorial: PHP video tutorial

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