How to debug input validation issues in PHP functions?

You can debug input validation issues in PHP functions through var_dump(), error_log(), breakpoints, exceptions, etc. to check the value of input variables, log error messages, execute code line by line, or throw exceptions.

#How to debug input validation issues in PHP functions?

Practical Case

The following PHP function verifies whether the data from the text field is a number:

function is_numeric($input) {
  if (!is_string($input)) {
    return false;
  }

  return ctype_digit($input);
}

Debugging Technology

1. Use var_dump()

var_dump() function can help you view the value of the input variable. For example:

$input = 'abc';

if (!is_numeric($input)) {
  var_dump($input);
}

This will print the following output:

string(3) "abc"

It can be seen that the variable is a string, not a number.

2. Use the error_log()

error_log() function to record information to the log file. For example:

$input = 'abc';

if (!is_numeric($input)) {
  error_log("Input '$input' is not numeric");
}

This will log an error message to your log file.

3. Set breakpoints

For more complex functions, you can use breakpoints to execute the code line by line and examine the values ​​of variables. Most IDEs support breakpoints, for example:

def is_numeric(input):
    if not isinstance(input, str):
        breakpoint()
        return False

    return input.isdigit()

When you reach a breakpoint, you can check the type and value of the input variable.

4. Using exceptions

If input validation fails, you can throw an exception. For example:

function is_numeric($input) {
  if (!is_string($input)) {
    throw new InvalidArgumentException("Input must be a string");
  }

  if (!ctype_digit($input)) {
    throw new InvalidArgumentException("Input must be numeric");
  }

  return true;
}

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