How to debug PHP custom functions?

There are many ways to debug PHP custom functions: Use the debug_backtrace() function to view the call stack. Use the var_dump() and print_r() functions to check variable values. Use the error_log() function to log error information to the log file. Use the xdebug extension for more advanced debugging, including breakpoint setting and step-by-step execution.

#How to debug PHP custom functions?

When developing PHP applications, custom functions are an essential tool for achieving code reuse and improving maintainability. However, when problems arise with custom functions, debugging can be a challenge. Here's how to debug a PHP custom function:

1. Use debug_backtrace()

debug_backtrace() The function returns Stack information of the calling function. By placing debug_backtrace() calls within a function, you can determine how the function was called, and the context in which it was called.

function my_function() {
  var_dump(debug_backtrace());
}

2. Use var_dump() and print_r()

##var_dump() and print_r() function can be used to print variable values ​​in order to check the input and output of the function.

function my_function($param) {
  var_dump($param);
}

3. Use the error_log()

error_log() function to allow error information to be logged to the log file . By calling error_log() within a function, error information can be logged for future review.

function my_function() {
  error_log("An error occurred in my_function");
}

4. Using xdebug

xdebug is an extension for debugging PHP code. It provides a rich toolset including a debugger, variable viewer and performance analyzer.

To use xdebug, it needs to be installed and configured in a PHP environment. You can then set breakpoints in the function and step through the code.

Practical Case

Consider the following custom function:

function add($a, $b) {
  if (!is_numeric($a) || !is_numeric($b)) {
    throw new Exception("Invalid input: both arguments must be numeric");
  }

  return $a + $b;
}

If this function does not perform the expected behavior, you can use the above debugging techniques to investigate.

For example, to print the input and output values:

function add($a, $b) {
  var_dump($a, $b);
  $result = $a + $b;
  var_dump($result);

  return $result;
}

By investigating the

var_dump() output, you can determine if bad input was passed or if the function did not evaluate as expected result.

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