How to debug code using PHP built-in functions?

PHP built-in debugging function: var_dump() displays variable details, type, value, structure. print_r() prints information in a more readable format, suitable for debugging complex data structures. error_log() records messages to the error log to facilitate recording debugging information, errors or warnings.

How to use PHP built-in functions to debug code

PHP provides several built-in functions to help you debug code. These functions are simple to use but save a lot of time and effort.

var_dump()

var_dump() The function displays information about a variable, including its type, value, and structure. This is useful for checking whether a variable contains an expected value or type.

$array = ['foo' => 'bar', 'baz' => 'qux'];

var_dump($array);

Output:

array(2) {
  ["foo"]=>
  string(3) "bar"
  ["baz"]=>
  string(3) "qux"
}

print_r()

print_r() The function is similar to var_dump(), but it prints the information in a more readable format. This is useful for debugging complex data structures.

$object = new stdClass();
$object->name = 'John Doe';
$object->age = 30;

print_r($object);

Output:

stdClass Object
(
    [name] => John Doe
    [age] => 30
)

error_log()

error_log() The function logs a message to the error log. This is useful for logging debugging information, errors or warnings.

error_log('调试信息：变量 $name 为空。');

Practical case

Suppose you have a function that counts the number of words in a string. However, this function returns incorrect results. You can use these PHP built-in functions to debug your code:

function word_count($string) {
    // 分割字符串成单词
    $words = explode(' ', $string);

    // 返回单词数量
    return count($words);
}

// 测试函数
$string = 'This is a test string.';
$result = word_count($string);

// 检查结果
if ($result != 5) {
    error_log('函数 word_count() 返回错误的结果。');
}

By logging debugging information using the error_log() function, you can easily pinpoint why a function returns incorrect results.

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