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php problem?

Richard Korts
on
I have a very simple php program (attached). It is linked to from another place.

In Firefox, I get the attached jpg.

In Chrome I get a blank screen.

I ran the php syntax through http://phpcodechecker.com/. No issues.

What's wrong?
clear_sess.php
php_issue.jpg
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Most Valuable Expert 2011
Top Expert 2016

Commented:
Please use the code snippet feature to post code samples here at E-E, thanks.
<?php
// clear_sess.php
function conv_date($x) {
		$d = explode("-", $x);
		$r = $d[1] . "/" . $d[2] . "/" . $d[0];
		return $r;
	}
include "db_connect.php";
session_start();
$qry = "SELECT * from users where uid = '" . $_SESSION['uid'] . "'";
$uid = $_SESSION['uid'];
$res = mysqli_query($link, $qry);
$nr = mysqli_num_rows($res);
$u = mysqli_fetch_array($res,MYSQLI_ASSOC);
session_unset();
$_SESSION['uid'] = $u['uid'];
//echo $u['firm_name'] . "<br>";
$_SESSION['firmname'] = $u['firm_name'];
$_SESSION['addr1'] = $u['addr1'];
$_SESSION['addr2'] = $u['addr2'];
$_SESSION['phone'] = $u['phone'];
$_SESSION['tester'] = $u['tester'];
$_SESSION['tg_make_model'] = $u['tg_make_model'];
$_SESSION['tg_sn'] = $u['tg_sn'];
$_SESSION['tg_date_cal'] = conv_date($u['tg_date_cal']);
$_SESSION['city_tester_no'] = $u['city_tester_no'];
if(! empty($_SERVER['HTTP_USER_AGENT'])){
		$useragent = $_SERVER['HTTP_USER_AGENT'];
		if( preg_match('@(iPad|iPod|iPhone|Android|BlackBerry|SymbianOS|SCH-M\d+|Opera Mini|Windows CE|Nokia|SonyEricsson|webOS|PalmOS)@', $useragent) ){
			$loc = "phone.php";
		}
	} else {
	$loc = "form.php";	
	}
header("Location: " . $loc);
exit;
?>

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Most Valuable Expert 2011
Top Expert 2016
Commented:
Questions...

1. Did the session start correctly?  How do you know this (either yes or no)?

2. Did the query work?  How do you know this (either yes or no)?

3. What is the purpose of session_unset() on line 15?

4. Was there a reason to not  use session_write_close() in this script?

5. Is there any meaning that we should understand from the comment on line 2?
Richard KortsBusiness Owner / Chief Developer

Author

Commented:
Ray,

I found the issue; the variable $loc was not set in the non iphone, etc. devices case. Therefore, the header("Location: " . $loc) could not work. Makes PERFECT sense that Chrome displays a blank page.

Because of your questions I put in a bunch of echos, they led me to the solution.

Richard
Most Valuable Expert 2011
Top Expert 2016

Commented:
Great!

A "standard" design pattern in almost any programming language is to assign the default variable values before any conditional code block that can change the variable values.  So something like this would be wise...
// SET DEFAULT VALUE TO REDIRECT TO THE HOME PAGE
$loc = '/';

// TEST USER AGENT FOR "PHONE" INDICATORS, CHOOSE REDIRECT PATH
$useragent = !empty($_SERVER['HTTP_USER_AGENT']) ? $_SERVER['HTTP_USER_AGENT'] : NULL;
if ( preg_match('@(iPad|iPod|iPhone|Android|BlackBerry|SymbianOS|SCH-M\d+|Opera Mini|Windows CE|Nokia|SonyEricsson|webOS|PalmOS)@', $useragent) ) {
    $loc = "phone.php";
} else {
    $loc = "form.php";  
}

// GOTO THE APPROPRIATE SCRIPT LOCATION
header("Location: " . $loc);

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Richard KortsBusiness Owner / Chief Developer

Author

Commented:
That's EXACTLY what I did.

I often do that but not consistently.

R