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Tweaked MySql Connection - Now Select Query's Fail

Posted on 2016-07-30
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Last Modified: 2016-08-01
Hi Guys'

Yes it me again ...

I've updated some of php pages to include an access control function which works great - super pleased about that! However, the code I've used seems to conflict with select queries I've previously written.

Can you tell me what causes the problem please if I post some examples below?

Previously my config.php file looked like this: -

<?php


	/* Access to the databse via link commands requires the $link statement
	in order for them to be successful, also the term "localhost" stops the $link
	failing in the event of a change in your IP Address.*/
	
	$link = mysqli_connect("localhost" , "user", "password", "DbName");


?>

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Now it includes some access control functions and the config file looks like this:

// CONNECTION AND SELECTION VARIABLES FOR THE DATABASE
$db_host = "localhost";
$db_name = "DbName";
$db_user = "user";
$db_word = "password";

// OPEN A CONNECTION TO THE DATA BASE SERVER AND SELECT THE DB
$mysqli = new mysqli($db_host, $db_user, $db_word, $db_name);

// DID THE CONNECT/SELECT WORK OR FAIL?
if ($mysqli->connect_errno)
{
    $err
    = "CONNECT FAIL: "
    . $mysqli->connect_errno
    . ' '
    . $mysqli->connect_error
    ;
    trigger_error($err, E_USER_ERROR);
}

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The first config allowed the following select queries to run: -

<?php
	
	$query = "select `partID`, `partDescription`, `qtyInStock`, `sales42D`,	`sales14D`, `supplierCompany`, `itemCost` FROM inventory";
	
	if ($result=mysqli_query($link, $query)) {
	
		while ($row = mysqli_fetch_array($result)) {
		
	?>
			<tr>
			<td><?php echo $row['partID'];?></td>
			<td><?php echo $row['partDescription'];?></td>
			<td><?php echo $row['qtyInStock'];?></td>
			<td><?php echo $row['sales42D'];?></td>
			<td><?php echo $row['sales14D'];?></td>
			<td><?php echo $row['supplierCompany'];?></td>
			<td><?php echo $row['itemCost'];?></td>
			</tr>
						
<?php
		}
	
	} else {
	
		echo "It failed!";
	
	}
?>

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The 2nd config files causes the connection to fail ... what am I doing wrong?

Thanks J
0
Comment
Question by:Ridgejp
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13 Comments
 
LVL 111

Expert Comment

by:Ray Paseur
ID: 41735680
Without a test case, we have to guess a little bit, but I think this is an educated guess.  

PHP has two ways of using the MySQLi extension.  One is procedural and one is object-oriented.  Details in the man pages here (for the connect() or __construct() functions):
http://php.net/manual/en/function.mysqli-connect.php
http://php.net/manual/en/mysqli.construct.php

As written, the functions return different variables.  
$link = mysqli_connect("localhost" , "user", "password", "DbName");
$mysqli = new mysqli($db_host, $db_user, $db_word, $db_name);

Since $link is not the same as $mysqli, the rest of the code cannot use $link or $mysqli interchangeably.  My recommendation is to use the object-oriented notation with $mysqli, and dispense with the procedural notation entirely.  The primary reason for this recommendation is that object-oriented programming is more susceptible to automated testing, and is more in line with modern design patterns.  Procedural programming kind of went into the rubbish bin at the end of the 20th century.  It's also easier to swap out the old, obsolete mysql statements for the object-oriented mysqli statements.

Details are available in this article, including tested-and-working examples.
https://www.experts-exchange.com/articles/11177/PHP-MySQL-Deprecated-as-of-PHP-5-5-0.html

It's also syntactically easier to use the object-oriented fetch method.  No need to flop back and forth between PHP and HTML.  Fewer fiddly punctuation marks means fewer parse errors, too.  Greater programmatic flexibility since the rows are returned in the form of objects instead of arrays.  Here's an easier and more efficient way to write the code (untested but probably correct in principle):
<?php
    
$query = "select `partID`, `partDescription`, `qtyInStock`, `sales42D`, `sales14D`, `supplierCompany`, `itemCost` FROM inventory";
    
if (!$result = $mysqli->query($query)) {
    trigger_error( /* FAILURE DIAGNOSTICS */, E_USER_ERROR);
}
while ($row = mysqli_fetch_object($result)) {
    $row = <<<EOD
            <tr>
            <td> $row->partID </td>
            <td> $row->partDescription </td>
            <td> $row->qtyInStock </td>
            <td> $row->sales42D </td>
            <td> $row->sales14D </td>
            <td> $row->supplierCompany </td>
            <td> $row->itemCost </td>
            </tr>
EOD;
    echo $row;
}

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0
 

Author Comment

by:Ridgejp
ID: 41735687
Hi Ray,

My query looks like this now, however, the pages fails to load at all ... did I do something wrong? Thanks for the links too more bedtime reading ... your section on access_control() was great!

</div>
		
		<table id="table" class="table table-striped">	
			<thead>
			<tr>
				
			
			<th class="success">partID</th>
			<th class="success">Description</th>
			<th class="success">stockQty</th>
			<th class="success">sales42D</th>
			<th class="success">sales14D</th>
			<th class="success">supplier</th>
			<th class="success">itemCost (£)</th>
			
			</tr>
			</thead>
			<tbody class="searchable">
			
<?php
    
$query = "select `partID`, `partDescription`, `qtyInStock`, `sales42D`, `sales14D`, `supplierCompany`, `itemCost` FROM inventory";
    
if (!$result = $mysqli->query($query)) {
    trigger_error( /* FAILURE DIAGNOSTICS */, E_USER_ERROR);
}
while ($row = mysqli_fetch_object($result)) {
    $row = <<<EOD
            <tr>
            <td> $row->partID </td>
            <td> $row->partDescription </td>
            <td> $row->qtyInStock </td>
            <td> $row->sales42D </td>
            <td> $row->sales14D </td>
            <td> $row->supplierCompany </td>
            <td> $row->itemCost </td>
            </tr>
EOD;
    echo $row;
}
		</table>
</div>

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0
 
LVL 111

Expert Comment

by:Ray Paseur
ID: 41735688
Sorry, my "cut and paste" mistake.  I never use the procedural code, and sometimes forget to ferret it out!  Try it like this (line 8, et seq):
<?php
    
$query = "select `partID`, `partDescription`, `qtyInStock`, `sales42D`, `sales14D`, `supplierCompany`, `itemCost` FROM inventory";
    
if (!$result = $mysqli->query($query)) {
    trigger_error( /* FAILURE DIAGNOSTICS */, E_USER_ERROR);
}
while ($row = $result->fetch_object()) {
    $tr = <<<EOD
            <tr>
            <td> $row->partID </td>
            <td> $row->partDescription </td>
            <td> $row->qtyInStock </td>
            <td> $row->sales42D </td>
            <td> $row->sales14D </td>
            <td> $row->supplierCompany </td>
            <td> $row->itemCost </td>
            </tr>
EOD;
    echo $tr;
}

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Also, you might want to include some kind of "failure diagnostics" instead of the comment.  If the query ever fails, you'll want to be aware of the issue.
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Author Comment

by:Ridgejp
ID: 41735865
Still no joy sorry ... although I've noticed that the opening table statement is no longer linked color-wise to the closing table statement. I'm using brackets to code my php.

Screenshot and code attached ...

<table id="table" class="table table-striped">	
			<thead>
			<tr>
				
			
			<th class="success">partID</th>
			<th class="success">Description</th>
			<th class="success">stockQty</th>
			<th class="success">sales42D</th>
			<th class="success">sales14D</th>
			<th class="success">supplier</th>
			<th class="success">itemCost (£)</th>
			
			</tr>
			</thead>
			<tbody class="searchable">
			
<?php
    
$query = "select `partID`, `partDescription`, `qtyInStock`, `sales42D`, `sales14D`, `supplierCompany`, `itemCost` FROM inventory";
    
if (!$result = $mysqli->query($query)) {
    trigger_error( /* FAILURE DIAGNOSTICS */, E_USER_ERROR);
}
while ($row = $result->fetch_object()) {
    $tr = <<<EOD
            <tr>
            <td> $row->partID </td>
            <td> $row->partDescription </td>
            <td> $row->qtyInStock </td>
            <td> $row->sales42D </td>
            <td> $row->sales14D </td>
            <td> $row->supplierCompany </td>
            <td> $row->itemCost </td>
            </tr>
EOD;
    echo $tr;
}
		</table>

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0
 

Author Comment

by:Ridgejp
ID: 41735867
0
 
LVL 111

Expert Comment

by:Ray Paseur
ID: 41735939
Well, we are still looking at fragments, so we need to do some diagnostics.  After the connection, please add var_dump($mysqli).  Then add the diagnostics in place of the comment, /* FAILURE DIAGNOSTICS */.  The general design for the diagnostics can be found in the article here:
https://www.experts-exchange.com/articles/11177/PHP-MySQL-Deprecated-as-of-PHP-5-5-0.html

In that article, look for the part about Create and Execute a SELECT Query.  You can copy the diagnostic code from the MySQLi example where it says "IF mysqli_query() RETURNS FALSE, LOG AND SHOW THE ERROR."  Hopefully, after we add the diagnostics to the script, we will get a signal of what went wrong and we can fix that.
1
 

Author Comment

by:Ridgejp
ID: 41737516
Is this correct now Ray - struggling a little with it?

</div>
		
		<table id="table" class="table table-striped">	
			<thead>
			<tr>
				
			
			<th class="success">partID</th>
			<th class="success">Description</th>
			<th class="success">stockQty</th>
			<th class="success">sales42D</th>
			<th class="success">sales14D</th>
			<th class="success">supplier</th>
			<th class="success">itemCost (£)</th>
			
			</tr>
			</thead>
			<tbody class="searchable">
			
<?php
    
$query = "select `partID`, `partDescription`, `qtyInStock`, `sales42D`, `sales14D`, `supplierCompany`, `itemCost` FROM inventory";
    
if (!$result = $mysqli->query($query)) {
    $err
    = "QUERY FAIL: "
    . $sql
    . ' ERRNO: '
    . $mysqli->errno
    . ' ERROR: '
    . $mysqli->error
    ;
    trigger_error($err, E_USER_ERROR);
}

var_dump($mysqli); 
                
while ($row = $result->fetch_object()) {
    $tr = <<<EOD
            <tr>
            <td> $row->partID </td>
            <td> $row->partDescription </td>
            <td> $row->qtyInStock </td>
            <td> $row->sales42D </td>
            <td> $row->sales14D </td>
            <td> $row->supplierCompany </td>
            <td> $row->itemCost </td>
            </tr>
EOD;
    echo $tr;
}
		</table>
</div>
       

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0
 
LVL 111

Expert Comment

by:Ray Paseur
ID: 41737584
Maybe a bit more like this (variable names have to be used consistently).  How does it test out?
</div>
        
        <table id="table" class="table table-striped">  
            <thead>
            <tr>
                
            
            <th class="success">partID</th>
            <th class="success">Description</th>
            <th class="success">stockQty</th>
            <th class="success">sales42D</th>
            <th class="success">sales14D</th>
            <th class="success">supplier</th>
            <th class="success">itemCost (£)</th>
            
            </tr>
            </thead>
            <tbody class="searchable">
            
<?php
    
$query = "select `partID`, `partDescription`, `qtyInStock`, `sales42D`, `sales14D`, `supplierCompany`, `itemCost` FROM inventory";
    
if (!$result = $mysqli->query($query)) {
    $err
    = "QUERY FAIL: "
    . $query
    . ' ERRNO: '
    . $mysqli->errno
    . ' ERROR: '
    . $mysqli->error
    ;
    trigger_error($err, E_USER_ERROR);
}
                
while ($row = $result->fetch_object()) {
    $tr = <<<EOD
            <tr>
            <td> $row->partID </td>
            <td> $row->partDescription </td>
            <td> $row->qtyInStock </td>
            <td> $row->sales42D </td>
            <td> $row->sales14D </td>
            <td> $row->supplierCompany </td>
            <td> $row->itemCost </td>
            </tr>
EOD;
    echo $tr;
}
        </table>
</div>

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0
 

Author Comment

by:Ridgejp
ID: 41737611
All changed ... but still not loading page. J
</div>
        
        <table id="table" class="table table-striped">  
            <thead>
            <tr>
                
            
            <th class="success">partID</th>
            <th class="success">Description</th>
            <th class="success">stockQty</th>
            <th class="success">sales42D</th>
            <th class="success">sales14D</th>
            <th class="success">supplier</th>
            <th class="success">itemCost (£)</th>
            
            </tr>
            </thead>
            <tbody class="searchable">
            
<?php
    
$query = "select `partID`, `partDescription`, `qtyInStock`, `sales42D`, `sales14D`, `supplierCompany`, `itemCost` FROM inventory";
    
if (!$result = $mysqli->query($query)) {
    $err
    = "QUERY FAIL: "
    . $query
    . ' ERRNO: '
    . $mysqli->errno
    . ' ERROR: '
    . $mysqli->error
    ;
    trigger_error($err, E_USER_ERROR);
}
                
while ($row = $result->fetch_object()) {
    $tr = <<<EOD
            <tr>
            <td> $row->partID </td>
            <td> $row->partDescription </td>
            <td> $row->qtyInStock </td>
            <td> $row->sales42D </td>
            <td> $row->sales14D </td>
            <td> $row->supplierCompany </td>
            <td> $row->itemCost </td>
            </tr>
EOD;
    echo $tr;
}
        </table>
</div>

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0
 
LVL 111

Accepted Solution

by:
Ray Paseur earned 2000 total points
ID: 41737658
Parse error on line 50, maybe?  It looks like you might need to close out PHP and go back to straight HTML there.

Are you using a framework or CMS in this application?
0
 

Author Comment

by:Ridgejp
ID: 41737797
Can't believe I missed that ... pop that in now and see what happens. I'm building each page from scratch piece by piece to replicate what my MS_Access Db achieves for my business so pushing myself a little so I guess that means I'm using framework as I'm not writing it within a Content Management System if that's what you mean?

Report back shortly ... thanks for sticking with me on this one.
J
0
 

Author Comment

by:Ridgejp
ID: 41737833
Bingo! Query loads successfully thanks for all your help - I just need to research what everything you included means so that I can better understand how to mod the other queries.

Thanks again ... J
0
 
LVL 111

Expert Comment

by:Ray Paseur
ID: 41737893
Glad to help, and best of luck with it! ~Ray
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