Introduction
An error is an expected or unexpected event that occurs when a PHP application runs. Every well-constructed PHP application should have error handling. An "expected" error can be a database query. An "unexpected" error is one that assumes a particular application state which, for some as yet unknown reason does not exist. So the PHP error and logging function allows error handling and logging. So I explain some of them in this article.
PHP debug_backtrace() function
The PHP debug_backtrace function generates a backtrace and it returns an array of associative arrays. The possible returned elements are:
| Name |
Type |
Description |
| function |
string |
The current function name. |
| line |
integer |
The current line number. |
| file |
string |
The current file name. |
| class |
string |
The current class name. |
| object |
object |
The current object. |
| type |
string |
The current call type and possible calls are:
- Returns: "->" - Method call
- Returns: "::" - Static method call
- Returns nothing - Function call
|
| args |
array |
If inside a function, this lists the functions arguments. If inside an included file, this lists the included file name. |
Syntax
Example
An example of the function is:
<?php
function one($str1, $str2)
{
two("bar", "wom");
}
function two($str1, $str2)
{
three("baz", "wom");
}
function three($str1, $str2)
{
print_r(debug_backtrace());
}
echo "<pre>";one
one("foo", "bar");
?>
As you can see, the script calls function one(), that calls two(), that calls three(). The debug_backtrace() will return an array of the steps.
Output
PHP debug_print_backtrace() function
The PHP debug_print_backtrace function prints a backtrace.
Syntax
Example
An example of the function is:
<?php
function foo($arg1, $arg2, $arg3)
{
bar();
}
function bar()
{
echo "<pre>";
print_r(debug_backtrace());
}
foo('one', 'two', 'three');
?>
Output
PHP error_get_last() function
The PHP error_get_last function gets the last error that occurred and it returns an associative array describing the last error with the key:
- "type" means error type.
- "message" means error message.
- "file" means the file where the error occurred.
- "line" means the line where the error occurred.
Syntax
Example
An example of the function is:
<?php
echo $var;
echo "<pre>";
print_r(error_get_last());
?>
Output
PHP error_reporting() function
The PHP error_reporting function specifies which errors are to be reported and it returns the old error_reporting level or the current level if no level parameter is given.
Syntax
| error_reporting(repoet_level) |
Parameter in error_reporting function
The parameter of the function is:
| Parameter |
Description |
| report_level |
It specifies the error report level for the current script. |
Example
An example of the function is:
<?php
error_reporting(E_ALL);
echo error_reporting()."</br>";
$old_error_reporting = error_reporting(error_reporting() ^ E_NOTICE);
echo error_reporting()."</br>";
error_reporting($old_error_reporting);
echo error_reporting();
?>
Output
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