Summary of causes and solutions for blank pages in php

This article mainly introduces the causes of blank pages in php and the summary of solutions. it is of great reference value for PHP program developers, for more information, see the case where many programmers encounter blank pages during php development, in php programming, a blank page may be caused by the following reasons:

1. logical error

Logical errors are the most difficult to eliminate. on the surface, the code may be legal and formal, but it is not unexpected to run. Why? Maybe it is not comprehensive enough for the author to think about it. after all, the person is a person, the computer is a computer, and it is impossible for the computer to run the script completely according to the person's ideas. Here, I would like to tell you a better debugging method, that is, to use the annotator "/**/" to comment out some code and observe the running conditions to eliminate errors one by one, finally, locate the error code. In this case, if you want to completely eliminate logical errors, you can't do it without patience.

2. the behavior is undefined.

See the following code:

<?php$action = $_GET['id'];if($action == '')$action = 1;if($action == 1) {echo("/$action's value is 1");} else if($action == 2) {echo("/$action's value is 2");}?>

You can understand this code, that is, if the $ action variable is empty, set it to 1, and then judge the value of the $ action variable to make different events. Of course, what will PHP do if $ action is neither 1 nor 2? The answer is-nothing will be done, so a blank page will be generated. Knowing the cause makes it easy to solve the problem. The solution to this problem is very simple. simply add an else after the if module and print some information.

3. Syntax error

You may ask, if a syntax error occurs, an error is Prompted. how can this problem be left blank? Of course, this is only a few examples. in some homepage spaces, if you write PHP with syntax errors, there will be no prompts. It is also easy to solve. before uploading a file, test it locally and find out the wrong code to correct it.

4. abuse the error blocker @

The error blocker "@" is often used in places where errors may occur. However, if the blocker is used too much or is not used frequently, it may also lead to blank spaces, let's take a look at the following two PHP scripts:

Test1.php:

<?php@include("test2.php");echo($var);?>

Test2.php:

<? Php $ var = "Hi" // this line of code has an error, no semicolon $ var1 = "Hello" // same as above?>

Run test1 and check that a blank page is displayed. Correction is also very easy. you can remove the prefix of the include function or correct the error in the test2.php file.