The error_reporting() function sets the error_reporting directive at runtime. PHP has many levels of errors, using this function sets that level for the duration (runtime) of your script.
The new error_reporting level. It takes on either a bitmask, or named constants. Using named constants is strongly encouraged to ensure compatibility for future versions. As error levels are added, the range of integers increases, so older integer-based error levels will not always behave as expected.
The available error level constants are listed below. The actual meanings of these error levels are described in the predefined constants.
Returns the old error_reporting level.
// Turn off all error reporting
// Report simple running errors
error_reporting(E_ERROR | E_WARNING | E_PARSE);
// Reporting E_NOTICE can be good too (to report uninitialized
// variables or catch variable name misspellings ...)
error_reporting(E_ERROR | E_WARNING | E_PARSE | E_NOTICE);
// Report all errors except E_NOTICE
// This is the default value set in php.ini
error_reporting(E_ALL ^ E_NOTICE);
// Report all PHP errors (bitwise 63 may be used in PHP 3)
// Same as error_reporting(E_ALL);
With PHP > 5.0.0
E_STRICT with value 2048 is
E_ALL does NOT
include error level
E_STRICT errors are evaluated at the
compile time thus such errors are not reported in the file where
error_reporting is enhanced