What are the characteristics of common errors in PHP functions?

Common error characteristics in PHP functions include: Error messages: Errors result in an error message or warning indicating the type and location of the error. Function parameter mismatch: The parameters passed do not match the number or types of parameters required by the function. Return type error: The returned value is not of the function's declared type. Undeclared function: The function is not declared or loaded before being used. Syntax error: A syntax error occurred in the function definition or call.

Common error characteristics in PHP functions

PHP functions are very useful during the development process, but when used incorrectly, May cause errors. Here are some characteristics of common errors in PHP functions:

• Error messages: Most PHP function errors result in an error message or warning. These messages usually indicate the type of error and where it occurred.
• Function parameter mismatch: A function may require a specific number or type of parameters. If the parameters passed are not what is expected, an error will be raised.
• Return type error: Some functions need to return a specific type of value. If the returned value is not of the expected type, an error is raised.
• Undeclared functions: Before using a function, it must be declared or loaded. Otherwise, errors will result.
• Syntax errors: Syntax errors in function definitions or calls can also cause errors.

Practical cases

The following are some actual cases of common errors in PHP functions:

• Error message:

  Fatal error: Uncaught Error: Call to a member function getArray() on a non-object in test.php on line 23

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This error indicates that the object does not exist or is not initialized when the getArray() method is called on line 23.

• Function parameter mismatch:

  function add($a, $b) {
  return $a + $b;
  }
  
  add(1, "2"); // 导致错误

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This error occurs because the second parameter passed is not a number, But a string.

• Return type error:

  function get_user(): string {
  return 123; // 导致错误
  }

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This error occurs because the function is declared to return a string type, but returns The value is a number.

• Undeclared function:

  calculate_average(array(1, 2, 3, 4)); // 导致错误

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This error occurs because the calculate_average function has not been declare or load.

• Syntax error:

  function multiply(a, b) { // 缺少参数声明
  return $a * $b;
  }

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This error occurs because a parameter type declaration is missing from the function definition.

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