PHP | Types of Errors

24 Aug, 2018
Error is the fault or mistake in a program. It can be several types. Error can occur due to wrong syntax or wrong logic. It is a type of mistakes or condition of having incorrect knowledge of the code.
There are various types of errors in PHP but it contains basically four main type of errors.
Parse error or Syntax Error: It is the type of error done by the programmer in the source code of the program. The syntax error is caught by the compiler. After fixing the syntax error the compiler compile the code and execute it. Parse errors can be caused dues to unclosed quotes, missing or Extra parentheses, Unclosed braces, Missing semicolon etcExample:<?php$x = "geeks";y = "Computer science";echo $x;echo $y;?>Error:PHP Parse error:  syntax error, unexpected '=' 
in /home/18cb2875ac563160a6120819bab084c8.php on line 3
Explanation: In above program, $ sign is missing in line 3 so it gives an error message.Fatal Error: It is the type of error where PHP compiler understand the PHP code but it recognizes an undeclared function. This means that function is called without the definition of function.Example:<?php  function add($x, $y){    $sum = $x + $y;    echo "sum = " . $sum;}$x = 0;$y = 20;add($x, $y);  diff($x, $y);?>Error:PHP Fatal error:  Uncaught Error: 
Call to undefined function diff() 
in /home/36db1ad4634ff7deb7f7347a4ac14d3a.php:12

Stack trace:
#0 {main}
  thrown in /home/36db1ad4634ff7deb7f7347a4ac14d3a.php on line 12
Explanation : In line 12, function is called but the definition of function is not available. So it gives error.Warning Errors : The main reason of warning errors are including a missing file. This means that the PHP function call the missing file.Example:<?php   $x = "GeeksforGeeks";  include ("gfg.php");  echo $x . "Computer science portal";?>Error:PHP Warning:  include(gfg.php): failed to 
open stream: No such file or directory in 
/home/aed0ed3b35fece41022f332aba5c9b45.php on line 5
PHP Warning:  include(): Failed opening 'gfg.php'
 for inclusion (include_path='.:/usr/share/php') in 
/home/aed0ed3b35fece41022f332aba5c9b45.php on line 5
Explanation: This program call an undefined file gfg.php which are not available. So it produces error.Notice Error: It is similar to warning error. It means that the program contains something wrong but it allows the execution of script.Example:<?php   $x = "GeeksforGeeks";  echo $x;  echo $geeks;?>Error:PHP Notice:  Undefined variable: geeks in 
/home/84c47fe936e1068b69fb834508d59689.php on line 5
Output:GeeksforGeeks
Explanation: This program use undeclared variable $geeks so it gives error message.
Parse error or Syntax Error: It is the type of error done by the programmer in the source code of the program. The syntax error is caught by the compiler. After fixing the syntax error the compiler compile the code and execute it. Parse errors can be caused dues to unclosed quotes, missing or Extra parentheses, Unclosed braces, Missing semicolon etcExample:<?php$x = "geeks";y = "Computer science";echo $x;echo $y;?>Error:PHP Parse error:  syntax error, unexpected '=' 
in /home/18cb2875ac563160a6120819bab084c8.php on line 3
Explanation: In above program, $ sign is missing in line 3 so it gives an error message.
<?php$x = "geeks";y = "Computer science";echo $x;echo $y;?>
Error:
PHP Parse error:  syntax error, unexpected '=' 
in /home/18cb2875ac563160a6120819bab084c8.php on line 3

Explanation: In above program, $ sign is missing in line 3 so it gives an error message.
Fatal Error: It is the type of error where PHP compiler understand the PHP code but it recognizes an undeclared function. This means that function is called without the definition of function.Example:<?php  function add($x, $y){    $sum = $x + $y;    echo "sum = " . $sum;}$x = 0;$y = 20;add($x, $y);  diff($x, $y);?>Error:PHP Fatal error:  Uncaught Error: 
Call to undefined function diff() 
in /home/36db1ad4634ff7deb7f7347a4ac14d3a.php:12

Stack trace:
#0 {main}
  thrown in /home/36db1ad4634ff7deb7f7347a4ac14d3a.php on line 12
Explanation : In line 12, function is called but the definition of function is not available. So it gives error.
<?php  function add($x, $y){    $sum = $x + $y;    echo "sum = " . $sum;}$x = 0;$y = 20;add($x, $y);  diff($x, $y);?>
Error:
PHP Fatal error:  Uncaught Error: 
Call to undefined function diff() 
in /home/36db1ad4634ff7deb7f7347a4ac14d3a.php:12

Stack trace:
#0 {main}
  thrown in /home/36db1ad4634ff7deb7f7347a4ac14d3a.php on line 12

Explanation : In line 12, function is called but the definition of function is not available. So it gives error.
Warning Errors : The main reason of warning errors are including a missing file. This means that the PHP function call the missing file.Example:<?php   $x = "GeeksforGeeks";  include ("gfg.php");  echo $x . "Computer science portal";?>Error:PHP Warning:  include(gfg.php): failed to 
open stream: No such file or directory in 
/home/aed0ed3b35fece41022f332aba5c9b45.php on line 5
PHP Warning:  include(): Failed opening 'gfg.php'
 for inclusion (include_path='.:/usr/share/php') in 
/home/aed0ed3b35fece41022f332aba5c9b45.php on line 5
Explanation: This program call an undefined file gfg.php which are not available. So it produces error.
<?php   $x = "GeeksforGeeks";  include ("gfg.php");  echo $x . "Computer science portal";?>
Error:
PHP Warning:  include(gfg.php): failed to 
open stream: No such file or directory in 
/home/aed0ed3b35fece41022f332aba5c9b45.php on line 5
PHP Warning:  include(): Failed opening 'gfg.php'
 for inclusion (include_path='.:/usr/share/php') in 
/home/aed0ed3b35fece41022f332aba5c9b45.php on line 5

Explanation: This program call an undefined file gfg.php which are not available. So it produces error.
Notice Error: It is similar to warning error. It means that the program contains something wrong but it allows the execution of script.Example:<?php   $x = "GeeksforGeeks";  echo $x;  echo $geeks;?>Error:PHP Notice:  Undefined variable: geeks in 
/home/84c47fe936e1068b69fb834508d59689.php on line 5
Output:GeeksforGeeks
Explanation: This program use undeclared variable $geeks so it gives error message.
<?php   $x = "GeeksforGeeks";  echo $x;  echo $geeks;?>
Error:
PHP Notice:  Undefined variable: geeks in 
/home/84c47fe936e1068b69fb834508d59689.php on line 5

Output:
GeeksforGeeks

Explanation: This program use undeclared variable $geeks so it gives error message.
PHP error constants and their description :
E_ERROR : A fatal error that causes script termination
E_WARNING : Run-time warning that does not cause script termination
E_PARSE : Compile time parse error.
E_NOTICE : Run time notice caused due to error in code
E_CORE_ERROR : Fatal errors that occur during PHP’s initial startup (installation)
E_CORE_WARNING : Warnings that occur during PHP’s initial startup
E_COMPILE_ERROR : Fatal compile-time errors indication problem with script.
E_USER_ERROR : User-generated error message.
E_USER_WARNING : User-generated warning message.
E_USER_NOTICE : User-generated notice message.
E_STRICT : Run-time notices.
E_RECOVERABLE_ERROR : Catchable fatal error indicating a dangerous error
E_DEPRECATED : Run-time notices.
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