mysqli_fetch_lengths()函數(shù)返回結(jié)果集中的字段長(zhǎng)度。
PHP結(jié)果對(duì)象（mysqli_result類）表示由SELECT或DESCRIBE或EXPLAIN查詢返回的MySQL結(jié)果。
mysqli_fetch_lengths()函數(shù)接受結(jié)果對(duì)象作為參數(shù)，檢索給定結(jié)果當(dāng)前行中列的長(zhǎng)度，并以數(shù)組形式返回它們。
mysqli_fetch_lengths($result);
| 序號(hào) | 參數(shù)及說明 |
|---|---|
| 1 | result(必需) 這是表示結(jié)果對(duì)象的標(biāo)識(shí)符。 |
PHP mysqli_fetch_lengths()函數(shù)返回一個(gè)數(shù)組（整數(shù)），該數(shù)組包含（當(dāng)前行的）每列的長(zhǎng)度/大小（如果成功），并且在出現(xiàn)錯(cuò)誤的情況下返回布爾值FALSE。
此函數(shù)最初是在PHP版本5中引入的，并且可以在所有更高版本中使用。
以下示例演示了mysqli_fetch_lengths()函數(shù)的用法（面向過程風(fēng)格）-
<?php
$con = mysqli_connect("localhost", "root", "password", "mydb");
mysqli_query($con, "CREATE TABLE myplayers(ID INT, First_Name VARCHAR(255), Last_Name VARCHAR(255), Place_Of_Birth VARCHAR(255), Country VARCHAR(255))");
print("創(chuàng)建表.....\n");
mysqli_query($con, "INSERT INTO myplayers values(1, 'Sikhar', 'Dhawan', 'Delhi', 'India')");
mysqli_query($con, "INSERT INTO myplayers values(2, 'Jonathan', 'Trott', 'CapeTown', 'SouthAfrica')");
mysqli_query($con, "INSERT INTO myplayers values(3, 'Kumara', 'Sangakkara', 'Matale', 'Srilanka')");
print("插入記錄.....\n");
//檢索表的內(nèi)容
$res = mysqli_query($con, "SELECT * FROM myplayers");
//行的長(zhǎng)度
$row = mysqli_fetch_row($res);
$lengths = mysqli_fetch_lengths($res);
print_r($lengths);
mysqli_free_result($res);
mysqli_close($con);
?>輸出結(jié)果
創(chuàng)建表..... 插入記錄..... Array ( [0] => 1 [1] => 6 [2] => 6 [3] => 5 [4] => 5 )
在面向?qū)ο箫L(fēng)格中，此函數(shù)的語法為$result->lengths;。以下是面向?qū)ο箫L(fēng)格中此函數(shù)的示例；
<?php
//建立連接
$con = new mysqli("localhost", "root", "password", "mydb");
$con -> query("CREATE TABLE Test(Name VARCHAR(255), AGE INT)");
$con -> query("insert into Test values('Raju', 25),('Rahman', 30),('Sarmista', 27)");
print("創(chuàng)建表.....\n");
$stmt = $con -> prepare( "SELECT * FROM Test WHERE Name in(?, ?)");
$stmt -> bind_param("ss", $name1, $name2);
$name1 = 'Raju';
$name2 = 'Rahman';
//執(zhí)行語句
$stmt->execute();
//檢索結(jié)果
$res = $stmt->get_result();
$row = $res->fetch_row();
$len = $res ->lengths;
print_r($len);
//結(jié)束語句
$stmt->close();
//關(guān)閉連接
$con->close();
?>輸出結(jié)果
創(chuàng)建表..... Array ( [0] => 4 [1] => 0 )
此函數(shù)要檢索長(zhǎng)度，必須在使用 mysqli_fetch_row 或 mysqli_fetch_array 或 mysqli_fetch_object 方法讀取行后調(diào)用，否則返回false：
<?php
$con = mysqli_connect("localhost", "root", "password", "mydb");
mysqli_query($con, "CREATE TABLE data(ID INT, Name VARCHAR(255), Age INT)");
mysqli_query($con, "INSERT INTO data values(1, 'Mohan', 25)");
mysqli_query($con, "INSERT INTO data values(2, 'Syamala', 36)");
print("插入記錄.....\n");
//檢索表的內(nèi)容
$res = mysqli_query($con, "SELECT * FROM data");
//行的長(zhǎng)度
$bool = $lengths = mysqli_fetch_lengths($res);
if($bool){
print("檢索到長(zhǎng)度");
}else{
print("失敗");
}
print_r($lengths);
mysqli_free_result($res);
mysqli_close($con);
?>輸出結(jié)果
插入記錄..... 失敗測(cè)試看看?/?