PHP basic syntax (file loading and error)

File Loading

There are 4 file-loaded syntax forms (note, not function):

Include, include_once, require, require_once;

their nature is the same, both for loading / importing / including / loading an external file into the current php code.

They only have a slight difference in 2 ways:

1, if the load file fails, there are different processing rules;include and require are different

2, if the load file duplication, there are different processing rules;XXX and xxx_once are different;

3, they are both grammatical structures, not functions, which can be used in two ways:

3.1 Include ' file path ';

3.2 Include (' File path ');

the difference between include_once and include : The former guarantees that it will not be loaded repeatedly

the difference between require and include :

If the included file does not exist, that is, if the reference fails (an error),include warns and continues execution of subsequent code ,require directly terminates.

Error Handling

Syntax error:

The program can not run, directly prompt syntax error.

Run-time error:

Errors that occur only if the program runs to a row, or is run in certain specific situations.

Logic error:

The program runs from start to finish without (and prompting) errors, but the results of the program run calculation are incorrect.

System error:

E_error: System Critical Error

Once it happens, the program stops executing immediately.

E_warning: System Warning

One occurs, prompts for errors, and continues execution.

E_parse: Syntax error

one occurs, the error is prompt, and the code does not run at all --check the syntax before running.

E_notice: System Tips

One occurs, prompts for errors, and continues execution.

user-defined error

There are only 3 of them:

E_user_error;

e_user_warning;

E_user_notice;

Is that the programmer "generates" an error by means of the program code .

Grammar:

Trigger_error (" error prompt " , user error code );

Incorrect Display control

Web page display (hint) error message, can be controlled, there are 2 ways:

1, in PHP. INI file, which is valid for all PHP programs;

2, in the current script file, only valid for the current Footstep file.

The error display has 2 aspects which can be controlled;

1, set whether to display:display_error:

PHP.ini ;display_error = on; // indicates display, Off means no display;

in the script: ini_set ("Display_error", 1); 1 indicates display, 0 means no display, or true,false

The set priority in the script is high.

2, set what level of error is displayed -dependent on the condition that the first item is set to display.

PHP. INI file:

error_reporting = E_notice; Show only e_notice Errors

error_reporting = E_notice | e_warning; show e_notice and e_warning Errors

error_reporting = E_notice | e_warning | E_user_error;

displays e_notice and e_warning and e_user_error Errors

Set in code:

Ini_set ("error_reporting", E_notice); Show only e_notice Errors

Ini_set ("error_reporting", E_notice | e_warning); show e_notice and e_warning Errors

Ini_set ("error_reporting", E_all | E_strict & ~e_notice); Turn off e_notice errors only

Ini_set () meaning can be set in almost all php.ini , in the form of the following:

Ini_set ("Set Item Name", value); // This setting is only valid for the current script, and it is convenient to restart Apachewithout rebooting.

Another corresponding function is:ini_get ("Set item Name");// used to get the value of an item.

Logging error Logs

in the development phase, we usually show all errors --Intent to resolve the error

in the product phase, we usually hide all errors -and simultaneously log error messages to a file-the error log file.

We can view the error log ourselves to resolve errors that were not found during the development phase.

There are also 2 ways to log error logs :

1, set in the php.ini file:

Log_errors = on; // used to set whether the error log is logged, on record,Off not recorded

Error_log = "Error log file name"; set the file name of the error log

At this point, the file does not have a given path, and the file is created under each folder and logged in.

Error_log also has a special value that can be used :

Error_log = syslog; instead of logging the error log file, the error message is written to the system error log

PHP basic syntax (file loading and error)