(PHP 5, PHP 7, PHP 8)
mysqli_result::$field_count -- mysqli_num_fields — Gets the number of fields in the result set
面向对象风格
过程化风格
Returns the number of fields in the result set.
result仅以过程化样式：由 mysqli_query()、mysqli_store_result()、 mysqli_use_result()、mysqli_stmt_get_result() 返回的结果集标识。
An int representing the number of fields.
Example #1 面向对象风格
<?php
mysqli_report(MYSQLI_REPORT_ERROR | MYSQLI_REPORT_STRICT);
$mysqli = new mysqli("localhost", "my_user", "my_password", "world");
$result = $mysqli->query("SELECT Name, CountryCode, District, Population FROM City ORDER BY ID LIMIT 1");
/* Get the number of fields in the result set */
$field_cnt = $result->field_count;
printf("Result set has %d fields.\n", $field_cnt);
Example #2 过程化风格
<?php
mysqli_report(MYSQLI_REPORT_ERROR | MYSQLI_REPORT_STRICT);
$link = mysqli_connect("localhost", "my_user", "my_password", "world");
$result = mysqli_query($link, "SELECT Name, CountryCode, District, Population FROM City ORDER BY ID LIMIT 1");
/* Get the number of fields in the result set */
$field_cnt = mysqli_num_fields($result);
printf("Result set has %d fields.\n", $field_cnt);
以上例程会输出：
Result set has 4 fields.