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Update Mysql Data with PHP Code not working

This code is supposed to allow me to view data in a mysql database & then allow me to edit it & submit it updating the database. I'm getting an error "attached in the photo"  when I go to the page in the browser.
$host="localhost"; // Host name 
$username="uname"; // Mysql username 
$password="password"; // Mysql password 
$db_name="test"; // Database name 
$tbl_name="test_mysql"; // Table name 

// Connect to server and select database.
mysql_connect("$host", "$username", "$password")or die("cannot connect"); 
mysql_select_db("$db_name")or die("cannot select DB");

// get value of id that sent from address bar

// Retrieve data from database 
$sql="SELECT * FROM $tbl_name WHERE id='$id'";

<table width="400" border="0" cellspacing="1" cellpadding="0">
<form name="form1" method="post" action="update_ac.php">
<table width="100%" border="0" cellspacing="1" cellpadding="0">
<td colspan="3"><strong>Update data in mysql</strong> </td>
<td align="center">&nbsp;</td>
<td align="center">&nbsp;</td>
<td align="center">&nbsp;</td>
<td align="center">&nbsp;</td>
<td align="center">&nbsp;</td>
<td align="center"><strong>Name</strong></td>
<td align="center"><strong>Lastname</strong></td>
<td align="center"><strong>Email</strong></td>
<td align="center"><input name="name" type="text" id="name" value="<? echo $rows['name']; ?>"></td>
<td align="center"><input name="lastname" type="text" id="lastname" value="<? echo $rows['lastname']; ?>" size="15"></td>
<td><input name="email" type="text" id="email" value="<? echo $rows['email']; ?>" size="15"></td>
<td><input name="id" type="hidden" id="id" value="<? echo $rows['id']; ?>"></td>
<td align="center"><input type="submit" name="Submit" value="Submit"></td>


// close connection 


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Lukasz Chmielewski

8/22/2022 - Mon
Ray Paseur

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Ray Paseur

Also, please let me suggest a really good book to help you get some foundation in how PHP and MySQL work together.  It will not make you a pro, but it has great examples and is very readable.  Also comes with a downloadable code library that you can copy and use for your own apps.

HTH, ~Ray
Chris Harte

Your query is not returning anything. Try this on line 19

$row_num = mysql_num_rows($result);
echo "number of rows returned $row_num";
Ray Paseur

@Munterman:  Actually the query is returning an error value.  The warning message is pretty clear.  MySQL_Query() returns either a results resource on success or FALSE on failure.  The message says, "... expects parameter 1 to be a resource, boolean given..."  In this case, the boolean is FALSE.

Man page here (see the return values):
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Lukasz Chmielewski

There are 3 possibilities of this error:
1. The name of the table is for non-existing one
2. There is no ?id=yournumber in the GET variable from the browser addressbar
3. Well, I forgot the 3rd one

Turn on error reporting as Ray told, it is essential to "debug" mysql/php errors
Lukasz Chmielewski

What was the cause ?