PHP/debugging - Revision history

Woozle: fx

2024-08-19T00:24:49Z

← Older revision		Revision as of 00:24, 19 August 2024
Line 30:		Line 30:
	===obsolete===		===obsolete===
	These were true in earlier versions of PHP, but behavior was changed in PHP 5 or maybe 7:		These were true in earlier versions of PHP, but behavior was changed in PHP 5 or maybe 7:
	* <s>If you pass an object to a function, the ~~function~~ will be operating on a ''copy'' of the object unless the function is called with the object passed as a reference: '''''CalledFunction''(&$''objName'');'''. The function declaration itself needs no modifications.</s>		* <s>If you pass an object to a function, the fundebug_print_backtrace()ction will be operating on a ''copy'' of the object unless the function is called with the object passed as a reference: '''''CalledFunction''(&$''objName'');'''. The function declaration itself needs no modifications.</s>
	* <s>If the function is expected to store the object for later use (e.g. it is a class constructor), the function must also use a reference when saving the object: '''$this->''localName'' =& $''iObjectParam'';'''. Otherwise (again) it will be using a copy, not the original.</s>		* <s>If the function is expected to store the object for later use (e.g. it is a class constructor), the function must also use a reference when saving the object: '''$this->''localName'' =& $''iObjectParam'';'''. Otherwise (again) it will be using a copy, not the original.</s>
			==Functions==
			* [https://www.php.net/manual/en/function.debug-backtrace.php <code>debug_backtrace()</code>]
			* [https://www.php.net/manual/en/function.debug-print-backtrace.php <code>debug_print_backtrace()</code>]
	==Error Messages==		==Error Messages==
	''some of these are not found in the PHP documentation''		''some of these are not found in the PHP documentation''

Woozle at 23:56, 14 June 2021

2021-06-14T23:56:29Z

← Older revision		Revision as of 23:56, 14 June 2021
Line 1:		Line 1:
	=Debugging PHP=		=Debugging PHP=
			* See [[/interactive]] for information about step-through debugging.
	==Blank Pages==		==Blank Pages==
	This code will cause most errors to generate page output, rather than just a blank page:		This code will cause most errors to generate page output, rather than just a blank page:

Woozle at 13:38, 13 June 2021

2021-06-13T13:38:36Z

← Older revision		Revision as of 13:38, 13 June 2021
Line 13:		Line 13:
	php -l {{arg\|name of PHP file}}		php -l {{arg\|name of PHP file}}

	==~~Newbie~~ Traps & Pitfalls==		==Traps & Pitfalls==
	PHP will let you get away with a lot of syntax mistakes which are perfectly valid code (often creating unexpected variables in the process) but not what you intended.		PHP will let you get away with a lot of syntax mistakes which are perfectly valid code (often creating unexpected variables in the process) but not what you intended.

Line 25:		Line 25:
	*** The "is equal to" comparison operator is "==", not "=".		*** The "is equal to" comparison operator is "==", not "=".
	**** You can, however, use the assignment operator ("=") within an expression, and the expression will evaluate to the result of the final assignment.		**** You can, however, use the assignment operator ("=") within an expression, and the expression will evaluate to the result of the final assignment.
			===undeclared variables===
			One of the few major weaknesses of PHP as a serious programming language is its lack of any way to require variable declaration before usage -- the equivalent of "use strict;" in [[Perl]] or "Option Explicit" in [[Visual Basic]]. [http://www.wellho.net/forum/Writing-PHP/use-strict.html Here] is a brief discussion of this problem, with a workaround which might be useful in some situations (but not if you need to turn off warnings for other reasons, such as needing to suppress messages about duplicate http headers).
	===obsolete===		===obsolete===
	These were true in earlier versions of PHP, but behavior was changed in PHP 5 or maybe 7:		These were true in earlier versions of PHP, but behavior was changed in PHP 5 or maybe 7:
	* <s>If you pass an object to a function, the function will be operating on a ''copy'' of the object unless the function is called with the object passed as a reference: '''''CalledFunction''(&$''objName'');'''. The function declaration itself needs no modifications.</s>		* <s>If you pass an object to a function, the function will be operating on a ''copy'' of the object unless the function is called with the object passed as a reference: '''''CalledFunction''(&$''objName'');'''. The function declaration itself needs no modifications.</s>
	* <s>If the function is expected to store the object for later use (e.g. it is a class constructor), the function must also use a reference when saving the object: '''$this->''localName'' =& $''iObjectParam'';'''. Otherwise (again) it will be using a copy, not the original.</s>		* <s>If the function is expected to store the object for later use (e.g. it is a class constructor), the function must also use a reference when saving the object: '''$this->''localName'' =& $''iObjectParam'';'''. Otherwise (again) it will be using a copy, not the original.</s>
			==Error Messages==
			''some of these are not found in the PHP documentation''
			* '''REG_EMPTY''': [[regex]]-related, but not sure what it means; it may reflect a difference between Perl-style regex (preg_* functions) and grep-style regex (ereg* functions). I changed the expression "('\|")" to "['"]", and this seemed to solve the problem.
			* '''REG_ERANGE''': This error appears to originate in the [[regex]] library, and means "Invalid character range, e.g. ending point is earlier in the collating order than the starting point." (Documented [http://www.laurikari.net/tre/api.html here])
			** In one case, this was caused by having a forward-slash ("/") in the bracketed list of possible characters; escaping the forward slash fixed the problem.

Woozle: Created page with "=Debugging PHP= ==Blank Pages== This code will cause most errors to generate page output, rather than just a blank page: $fErrLevel = E_ALL; error_r..."

2021-06-13T13:35:56Z

Created page with "=Debugging PHP= ==Blank Pages== This code will cause most errors to generate page output, rather than just a blank page: <syntaxhighlight lang=php> $fErrLevel = E_ALL; error_r..."

New page

=Debugging PHP=
==Blank Pages==
This code will cause most errors to generate page output, rather than just a blank page:
<syntaxhighlight lang=php>
$fErrLevel = E_ALL;
error_reporting($fErrLevel);
if (!ini_get('display_errors')) {
ini_set('display_errors', 'TRUE');
}
</syntaxhighlight>

Some errors will crash PHP completely, causing a blank page even with error_reporting turned on; this command ([https://toot.cat/@js0000/106377779222214992 h/t]) will show even those:
php -l {{arg|name of PHP file}}

==Newbie Traps & Pitfalls==
PHP will let you get away with a lot of syntax mistakes which are perfectly valid code (often creating unexpected variables in the process) but not what you intended.

Here are some mistakes I made when re-learning PHP in 2005 after not using it since 1997, most of which produced no immediate error messages; the code simply wouldn't work, and it took me several edit-upload-run cycles to find each problem:
* '''Classes''':
** Member vars and functions must ''always'' be referred to using '''$this->''FunctionName''()'''
** However, var members do not take a $ prefix: '''$this->''varName'''''
** In a child function ('''class''' <u>child</u> '''extends''' <u>parent</u>), if the parent has member variables declared as "private" and you attempt to access them with $this->varname, PHP will silently create ''new'' member variables for the child scope rather than referencing the old ones or generating an error. (Change the var declarations to "protected".)
* '''Operators''':
** As in C/[[C++]]:
*** The "is equal to" comparison operator is "==", not "=".
**** You can, however, use the assignment operator ("=") within an expression, and the expression will evaluate to the result of the final assignment.
===obsolete===
These were true in earlier versions of PHP, but behavior was changed in PHP 5 or maybe 7:
* <s>If you pass an object to a function, the function will be operating on a ''copy'' of the object unless the function is called with the object passed as a reference: '''''CalledFunction''(&$''objName'');'''. The function declaration itself needs no modifications.</s>
* <s>If the function is expected to store the object for later use (e.g. it is a class constructor), the function must also use a reference when saving the object: '''$this->''localName'' =& $''iObjectParam'';'''. Otherwise (again) it will be using a copy, not the original.</s>