In this article, I will discuss the types of errors in PHP and how to deal with them.
There are four types of errors that a PHP script can generate.
- Syntax errors or compilation errors
- Runtime errors or fatal errors
- Warnings
- Notice of errors
Syntax errors (compilation errors)
Syntax errors are errors detected by the compiler. These errors result from misspelling, missing semicolon, incorrectly ending string, or any other typing error. When the compiler encounters such an error, it reports these errors as syntax errors. The following code shows the syntax errors in lin2 and line 6.
<?php
$a="hello";
$b='world!
echo $a;
echo '<br>';
ech $b;
?>Production
When we make a correction to line 2 of the above program like $b=’world!’ we get another error. This is caused by a misspelling in the echo function in the last line.
Once we fixed these two errors as follows, we get the following output.
<?php
$a="hello";
$b='world!';
echo $a;
echo '<br>';
echo $b;
?>Production
Notice of errors
In fact, a notification error may or may not be an error. These are minor errors. Also, notification errors do not stop the script and produce the output. The most common source notification errors are the use of an undefined variable. As can be seen in the following code, the variables a, b and c are not defined. So when we try to print these variables, a notification error occurs.
<?php
echo $a.' '.$b.' '.$c;
?>Production
Runtime errors (fatal errors)
These errors cause the script to crash. When a fatal error occurs, the script stops running. These types of errors come from several sources. For example, call a non-existent function or call a function from an object that does not exist.
Examples of Types of Errors in PHP and How to Handle Them
The following code shows that calling a non-existent mysqli function results in a fatal error.
<?php
// Try to connect with a MySQL database
$con1=mysqli("localhost", "root", "", "somedatabase");
?>Production
Also, the following error occurs because of the undefined show() function.
<?php
class MyClass
{
protected $a, $b;
}
class SubClass extends MyClass{
function __construct()
{
$this->a=1; $this->b=2;
show();
}
function show()
{
echo 'a=", $this->a;
echo "<br>b = ", $this->b;
}
}
$ob=new SubClass(20, 30);
$ob->__construct();
?>Production
Fix the above error
In order to fix the above error, simply call the show() function as an instance method as shown below.
<?php
class MyClass
{
protected $a, $b;
}
class SubClass extends MyClass{
function __construct()
{
$this->a=1; $this->b=2;
$this->show();
}
function show()
{
echo "a=", $this->a;
echo "<br>b = ", $this->b,"<br>';
}
}
$ob=new SubClass(20, 30);
$ob->__construct();
?>Production
The following fatal error results from the fact that the database table ’emp’ does not exist.
<?php
// Try to connect with a MySQL database
$con1=new mysqli("localhost", "root", "", "d1");
$r1=$con1->query('select * from emp');
$row = $r1->fetch_assoc()
?>Production
When a recursive function fails to complete, a runtime error occurs. The following code demonstrates this.
<?php
function f1()
{
$a=$a++;
echo $a;
f1();
}
f1();
?>Production
Warnings
Warnings indicate the presence of certain problems. However, they do not stop script execution. The following code displays a warning generated when the database user cannot access a table due to invalid credentials.
<?php
// Try to connect with a MySQL database
$con1=new mysqli("localhost", "someuser", "123456", "somedatabase");
?>Production
Similarly, the following code generates a warning due to an invalid database name.
<?php
// Try to connect with a MySQL database
$con1=new mysqli("localhost", "root", "", "somedatabase");
?>Production
Further reading
Introducing the Medium Stack
Building Single Page Applications with Angular
Angular 10 Binding data in different ways
Create Angular Components
Examples of array functions in PHP
Basic programs in PHP
