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错误“mysqli_num_rows”[重复](Error “mysqli_num_rows” [duplicate])

 
  这个问题在这里已有答案：  
  
   mysql_fetch_array（）/ mysql_fetch_assoc（）/ mysql_fetch_row（）/ mysql_num_rows等...期望参数1为资源 31答案  
  
 
 我该如何解决这个错误？  
 edit.php：  
 
  
  					<?php
   include 'connect.php';

   if(isset($_POST['btn_submit'])){
	
   }
   $cpf = '';
   $nome = '';
   $cep = '';
   if(isset($_GET['cpf'])){
	$sql = "select cpf, nome, cep from pessoas
		where cpf=" .$_GET['cpf'];
	$result = mysqli_query($con, $sql);
	if(mysqli_num_rows($result) > 0){
		$row = mysqli_fetch_assoc($result) ;
		$cpf = $row['cpf'];
		echo $cpf;
	}
   }
	
?> 
  
 
 
 错误：  
Warning: mysqli_num_rows() expects parameter 1 to be 
mysqli_result, boolean given in 
C:\xampp\htdocs\Banco_de_dados\edit.php on line 158
 
 Connect.php：  
 
  
  <?php
$servername = "localhost";
$username = "root";
$password = "";
$dbname = "meubd";
// Create connection
$con = mysqli_connect($servername, $username, $password, $dbname);
// Check connection
if ($con->connect_error) {
	die("Connection failed: " . $con->connect_error);
}
$sql = "SELECT nome, cpf, cep, rua, bairro, cidade, estado, ibge FROM pessoas";
$result = $con->query($sql);
?> 
  
 

 
 This question already has an answer here: 
  
   mysql_fetch_array()/mysql_fetch_assoc()/mysql_fetch_row()/mysql_num_rows etc… expects parameter 1 to be resource or result  32 answers   
  
 
How do I fix this error ? 
edit.php:  
 
  
  					<?php
   include 'connect.php';

   if(isset($_POST['btn_submit'])){
	
   }
   $cpf = '';
   $nome = '';
   $cep = '';
   if(isset($_GET['cpf'])){
	$sql = "select cpf, nome, cep from pessoas
		where cpf=" .$_GET['cpf'];
	$result = mysqli_query($con, $sql);
	if(mysqli_num_rows($result) > 0){
		$row = mysqli_fetch_assoc($result) ;
		$cpf = $row['cpf'];
		echo $cpf;
	}
   }
	
?> 
  
 
 
ERROR: 
Warning: mysqli_num_rows() expects parameter 1 to be 
mysqli_result, boolean given in 
C:\xampp\htdocs\Banco_de_dados\edit.php on line 158
 
Connect.php:  
 
  
  <?php
$servername = "localhost";
$username = "root";
$password = "";
$dbname = "meubd";
// Create connection
$con = mysqli_connect($servername, $username, $password, $dbname);
// Check connection
if ($con->connect_error) {
	die("Connection failed: " . $con->connect_error);
}
$sql = "SELECT nome, cpf, cep, rua, bairro, cidade, estado, ibge FROM pessoas";
$result = $con->query($sql);
?> 
  
 

原文：https://stackoverflow.com/questions/37114152

更新时间：2023-09-16 10:09

最满意答案

 不。调用命名函数会花费变量查找（如果不是全局则便宜）和函数调用。 将命名函数传递给另一个函数只需要一个变量查找。  
 下面是在方形免费shell中Chrome上运行的一些微基准测试。 用一粒盐来衡量所有基准。  
(function () {
  function f() { }
  var a = [1, 2, 3, 4, 5, 6];
  var t0 = Date.now();
  for (var i = 100000; --i >= 0;) { a.map(f); }
  var t1 = Date.now();
  print(t1 - t0);
})() 

24

(function () {
  var a = [1, 2, 3, 4, 5, 6];
  var t0 = Date.now();
  for (var i = 100000; --i >= 0;) { a.map(function f() {}); }
  var t1 = Date.now();
  print(t1 - t0);
})() 

29
 
 传递命名函数比传递匿名函数更快，因为每个循环条目都会重复实例化匿名函数。 

No. Calling a named function costs a variable lookup (cheap if not global) and a function call. Passing a named function to another function costs just a variable lookup. 
Below are some micro-benchmarks run on Chrome in the square free shell. Take all benchmarks with a grain of salt. 
(function () {
  function f() { }
  var a = [1, 2, 3, 4, 5, 6];
  var t0 = Date.now();
  for (var i = 100000; --i >= 0;) { a.map(f); }
  var t1 = Date.now();
  print(t1 - t0);
})() 

24

(function () {
  var a = [1, 2, 3, 4, 5, 6];
  var t0 = Date.now();
  for (var i = 100000; --i >= 0;) { a.map(function f() {}); }
  var t1 = Date.now();
  print(t1 - t0);
})() 

29
 
Passing the named function is faster than passing the anonymous function possibly because the anonymous function is instantiated repeatedly per loop entry.

错误“mysqli_num_rows”[重复](Error “mysqli_num_rows” [duplicate])

最满意答案

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