The key to debugging PHP functions is to master practical methods and tools. 1. First check whether the input parameters are correct, use var_dump or print_r to print parameter values, and confirm whether the type, format and default values ??are reasonable; 2. Turn on error reports (error_reporting and display_errors), display all error messages, and help position variables undefined and keys, etc.; 3. Segmented test logic, and determine whether the code execution process and intermediate results are in line with expectations through temporary output or logging; 4. Use debugging tools such as Xdebug to cooperate with IDE to achieve breakpoint debugging, single-step execution, etc. to improve efficiency; 5. Maintain good code specifications to reduce debugging difficulties caused by confusing naming or unclear function responsibilities.

Debugging a PHP function is actually not difficult, the key is to master several practical methods and tools. When a function does not run as expected, we usually need to check input and output, process logic, error prompts and other aspects. Below are some commonly used debugging techniques in actual operations.

Check whether the input parameters of the function are correct

Many times the function errors because the parameters passed in are incorrect. For example, the type does not match, the value is empty, or the format is incorrect.

• You can print the passed parameters at the beginning of the function with var_dump($param) or print_r($param) to confirm whether they are the value you expect.
• If it is an array or object, print_r() is more suitable than echo because it can display the structure.
• Note check whether the optional parameters have default values ??and whether they are accidentally overwritten.

For example:

 function addNumbers($a, $b) {
    var_dump($a, $b); // Check if it is a number return $a $b;
}

Use error reports to locate problems

Sometimes PHP does not report an error directly, especially in production environments, where the error message may be closed.

• In the development environment, it is recommended to enable error reporting:

   error_reporting(E_ALL);
  ini_set('display_errors', 1);

• This allows PHP to display all errors, including Notice and Warning, which helps quickly identify problems.

Common errors such as calling undefined variables, accessing non-existent array keys, spelling errors in function names, etc., will be exposed through these settings.

Segmented test function logic

If the function is long and contains multiple steps, you can comment out part of the code step by step, or insert temporary output statements to observe the execution process.

• For example, add an echo 'Step 1 passed'; to confirm whether a certain piece of code has been executed.
• Or print out the intermediate results to see if they meet expectations.
• For complex judgment logic, logging (such as writing to files) can also be used instead of echo to avoid damaging the page structure.

For example:

 if ($condition) {
    $result = doSomething();
    file_put_contents('debug.log', "Result after doSomething: $result\n", FILE_APPEND);
}

More efficient with debugging tools

If you often write PHP, it is recommended to be familiar with some debugging tools, which can greatly improve efficiency.

• Xdebug is the most commonly used PHP debugging extension. It can realize breakpoint debugging, single-step execution, viewing variables and other functions in conjunction with IDEs (such as PhpStorm, VS Code).
• If you don't want to install plug-ins, you can also use the online debugger or log analysis tool to assist in troubleshooting problems.
• Maintaining good code specifications during development can also help reduce debugging time, such as clear naming and single function responsibilities.

Basically these methods are all. Although it seems simple, many novices tend to ignore one or two of the details, resulting in low debugging efficiency.

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