What does the PHP error message Notice Use of undefined constant mean

Question

PHP is writing this error in the logs   Notice  Use of undefined constant    Error in logs   PHP Notice   Use of undefined constant department - assumed  department   line 5  PHP Notice   Use of undefined constant name - assumed  name   line 6  PHP Notice   Use of undefined constant email - assumed  email   line 7  PHP Notice   Use of undefined constant message - assumed  message   line 8    Relevant lines of code    department   mysql real escape string   POST department     name   mysql real escape string   POST name     email   mysql real escape string   POST email     message   mysql real escape string   POST message      What does it mean and why am I seeing it

User · Answer

Looks like the predefined fetch constants went away with the MySQL extension, so we need to add them before the first function...

//predifined fetch constants

define('MYSQL_BOTH',MYSQLI_BOTH);
define('MYSQL_NUM',MYSQLI_NUM);
define('MYSQL_ASSOC',MYSQLI_ASSOC);

I tested and succeeded.

User · Answer

You missed putting single quotes around your array keys        POST email    should be        POST  email

User · Answer

The correct way of using post variables is   lt  php   department     POST  department       gt    Use single quotation

User · Answer

Insert single quotes   Example   department   mysql real escape string   POST  department      name   mysql real escape string   POST  name      email   mysql real escape string   POST  email      message   mysql real escape string   POST  message

User · Answer

You should quote your array keys    department   mysql real escape string   POST  department      name   mysql real escape string   POST  name      email   mysql real escape string   POST  email      message   mysql real escape string   POST  message       As is  it was looking for constants called department  name  email  message  etc  When it doesn t find such a constant  PHP  bizarrely  interprets it as a string   department   etc    Obviously  this can easily break if you do defined  such a constant later  though it s bad style to have lower-case constants

User · Answer

The error message is due to the unfortunate fact that PHP will implicitly declare an unknown token as a constant string of the same name   That is  it s trying to interpret this  note the missing quote marks       POST department    The only valid way this would be valid syntax in PHP is if there was previously a constant department defined   So sadly  rather than dying with a Fatal error at this point  it issues this Notice and acts as though a constant had been defined with the same name and value      Implicit declaration of constant called department with value  department  define  department    department        There are various ways you can get this error message  but they all have the same root cause - a token that could be a constant   Strings missing quotes    my array bad key   This is what the problem is in your case  and it s because you ve got string array keys that haven t been quoted   Fixing the string keys will fix the bug   Change    department   mysql real escape string   POST department        etc       To    department   mysql real escape string   POST  department         etc       Variable missing dollar sign  var without dollar  Another reason you might see this error message is if you leave off the   from a variable  or  this- gt  from a member   Eg  either of the following would cause a similar error message   my local       should be  my local my member      should be  this- gt my member   Invalid character in variable name   bad-variable-name  A similar but more subtle issue can result if you try to use a disallowed character in a  variable name - a hyphen  -  instead of an underscore   would be a common case   For example  this is OK  since underscores are allowed in variable names   if  123      my var      do something        But this isn t   if  123      my-var      do something        It ll be interpreted the same as this   if  123      my - var        variable  my minus constant  var    do something        Referring to a class constant without specifying the class scope  In order to refer to a class constant you need to specify the class scope with     if you miss this off PHP will think you re talking about a global define     Eg   class MyClass     const MY CONST   123     public function my method         return self  MY CONST      This is fine         public function my method         return MyClass  MY CONST      This is fine        public function my bad method         return MY CONST      BUG - need to specify class scope         Using a constant that s not defined in this version of PHP  or is defined in an extension that s not installed  There are some system-defined constants that only exist in newer versions of PHP  for example the mode option constants for round   such as PHP ROUND HALF DOWN only exist in PHP 5 3 or later   So if you tried to use this feature in PHP 5 2  say    rounded   round  my var  0  PHP ROUND HALF DOWN     You d get this error message      Use of undefined constant PHP ROUND HALF DOWN - assumed    PHP ROUND HALF DOWN  Warning  2   Wrong parameter count for round

User · Answer

you probably forgot to use       For exemple     array text      var    change to     array  text       var

User · Answer

lt  php      test   test information     echo  test    gt       Notice  Use of undefined constant test - assumed  test  in D  xampp htdocs sp test envoirnmentVariables php on line 3   test information

User · Answer

Am not sure if there is any difference am using code igniter and i use    for the names and it works great    department   mysql real escape string   POST  department      name   mysql real escape string   POST  name      email   mysql real escape string   POST  email      message   mysql real escape string   POST  message       regards   Jorge

[php] What does the PHP error message "Notice: Use of undefined constant" mean?

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