(PHP 5, PHP 7, PHP 8)
mysqli_result::$lengths -- mysqli_fetch_lengths — Returns the lengths of the columns of the current row in the result set
面向对象风格
过程化风格
The mysqli_fetch_lengths() function returns an array containing the lengths of every column of the current row within 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 array of integers representing the size of each column (not including
any terminating null characters). false if an error occurred.
mysqli_fetch_lengths() is valid only for the current
row of the result set. It returns false if you call it before calling
mysqli_fetch_row/array/object or after retrieving all rows in the result.
Example #1 面向对象风格
<?php
$mysqli = new mysqli("localhost", "my_user", "my_password", "world");
/* check connection */
if (mysqli_connect_errno()) {
printf("Connect failed: %s\n", mysqli_connect_error());
exit();
}
$query = "SELECT * from Country ORDER BY Code LIMIT 1";
if ($result = $mysqli->query($query)) {
$row = $result->fetch_row();
/* display column lengths */
foreach ($result->lengths as $i => $val) {
printf("Field %2d has Length %2d\n", $i+1, $val);
}
$result->close();
}
/* close connection */
$mysqli->close();
?>
Example #2 过程化风格
<?php
$link = mysqli_connect("localhost", "my_user", "my_password", "world");
/* check connection */
if (mysqli_connect_errno()) {
printf("Connect failed: %s\n", mysqli_connect_error());
exit();
}
$query = "SELECT * from Country ORDER BY Code LIMIT 1";
if ($result = mysqli_query($link, $query)) {
$row = mysqli_fetch_row($result);
/* display column lengths */
foreach (mysqli_fetch_lengths($result) as $i => $val) {
printf("Field %2d has Length %2d\n", $i+1, $val);
}
mysqli_free_result($result);
}
/* close connection */
mysqli_close($link);
?>
以上例程会输出：
Field 1 has Length 3 Field 2 has Length 5 Field 3 has Length 13 Field 4 has Length 9 Field 5 has Length 6 Field 6 has Length 1 Field 7 has Length 6 Field 8 has Length 4 Field 9 has Length 6 Field 10 has Length 6 Field 11 has Length 5 Field 12 has Length 44 Field 13 has Length 7 Field 14 has Length 3 Field 15 has Length 2