zend_error()

zend_error() can be used to generate error messages. This function accepts two arguments; the first is the error type (see zend_errors.h), and the second is the error message.
zend_error(E_WARNING, "This function has been called with empty arguments");
Table 36-1 shows a list of possible values (see Figure 36-1). These values are also referred to in php.ini. Depending on which error type you choose, your messages will be logged.

Table 36-1. Zend's Predefined Error Messages.

ErrorDescription
E_ERROR Signals an error and terminates execution of the script immediately .
E_WARNING Signals a generic warning. Execution continues.
E_PARSE Signals a parser error. Execution continues.
E_NOTICE Signals a notice. Execution continues. Note that by default the display of this type of error messages is turned off in php.ini.
E_CORE_ERROR Internal error by the core; shouldn't be used by user-written modules.
E_COMPILE_ERROR Internal error by the compiler; shouldn't be used by user-written modules.
E_COMPILE_WARNING Internal warning by the compiler; shouldn't be used by user-written modules.

Figure 36-1. Display of warning messages in the browser.